extmod/vfs_fat: Add chdir() method.
extmod/vfs_fat: Add chdir() method.

Ported from stmhal.

henriknelson/micropython,hosaka/micropython,AriZuu/micropython,jmarcelino/pycom-micropython,mhoffma/micropython,ganshun666/micropython,dinau/micropython,selste/micropython,mpalomer/micropython,AriZuu/micropython,blazewicz/micropython,chrisdearman/micropython,adafruit/circuitpython,SHA2017-badge/micropython-esp32,selste/micropython,cwyark/micropython,dmazzella/micropython,trezor/micropython,tuc-osg/micropython,turbinenreiter/micropython,cwyark/micropython,bvernoux/micropython,tobbad/micropython,Timmenem/micropython,kerneltask/micropython,alex-robbins/micropython,redbear/micropython,Peetz0r/micropython-esp32,emfcamp/micropython,micropython/micropython-esp32,cwyark/micropython,MrSurly/micropython,adafruit/micropython,Peetz0r/micropython-esp32,infinnovation/micropython,matthewelse/micropython,puuu/micropython,deshipu/micropython,hiway/micropython,matthewelse/micropython,ganshun666/micropython,mhoffma/micropython,MrSurly/micropython-esp32,MrSurly/micropython,lowRISC/micropython,oopy/micropython,dxxb/micropython,henriknelson/micropython,adafruit/circuitpython,MrSurly/micropython-esp32,adafruit/circuitpython,redbear/micropython,kerneltask/micropython,pozetroninc/micropython,oopy/micropython,ryannathans/micropython,SHA2017-badge/micropython-esp32,pfalcon/micropython,MrSurly/micropython-esp32,AriZuu/micropython,turbinenreiter/micropython,Timmenem/micropython,pfalcon/micropython,pozetroninc/micropython,lowRISC/micropython,TDAbboud/micropython,torwag/micropython,henriknelson/micropython,ryannathans/micropython,puuu/micropython,kerneltask/micropython,chrisdearman/micropython,matthewelse/micropython,tobbad/micropython,mhoffma/micropython,selste/micropython,alex-march/micropython,turbinenreiter/micropython,turbinenreiter/micropython,trezor/micropython,MrSurly/micropython,Timmenem/micropython,dmazzella/micropython,pramasoul/micropython,tralamazza/micropython,HenrikSolver/micropython,hiway/micropython,alex-march/micropython,tralamazza/micropython,chrisdearman/micropython,mhoffma/micropython,swegener/micropython,Peetz0r/micropython-esp32,adafruit/micropython,toolmacher/micropython,deshipu/micropython,alex-robbins/micropython,cwyark/micropython,ganshun666/micropython,emfcamp/micropython,SHA2017-badge/micropython-esp32,PappaPeppar/micropython,alex-robbins/micropython,HenrikSolver/micropython,tuc-osg/micropython,emfcamp/micropython,TDAbboud/micropython,mpalomer/micropython,Peetz0r/micropython-esp32,HenrikSolver/micropython,trezor/micropython,tuc-osg/micropython,alex-march/micropython,puuu/micropython,TDAbboud/micropython,MrSurly/micropython,bvernoux/micropython,Peetz0r/micropython-esp32,PappaPeppar/micropython,dmazzella/micropython,jmarcelino/pycom-micropython,emfcamp/micropython,TDAbboud/micropython,kerneltask/micropython,swegener/micropython,redbear/micropython,dinau/micropython,pozetroninc/micropython,alex-robbins/micropython,trezor/micropython,redbear/micropython,lowRISC/micropython,micropython/micropython-esp32,pramasoul/micropython,dxxb/micropython,Timmenem/micropython,adafruit/micropython,emfcamp/micropython,infinnovation/micropython,tuc-osg/micropython,selste/micropython,jmarcelino/pycom-micropython,hosaka/micropython,PappaPeppar/micropython,torwag/micropython,dxxb/micropython,AriZuu/micropython,deshipu/micropython,ganshun666/micropython,torwag/micropython,matthewelse/micropython,pfalcon/micropython,pramasoul/micropython,ryannathans/micropython,micropython/micropython-esp32,ryannathans/micropython,PappaPeppar/micropython,matthewelse/micropython,tralamazza/micropython,adafruit/circuitpython,henriknelson/micropython,ganshun666/micropython,infinnovation/micropython,kerneltask/micropython,PappaPeppar/micropython,toolmacher/micropython,oopy/micropython,hiway/micropython,alex-march/micropython,blazewicz/micropython,redbear/micropython,alex-robbins/micropython,dxxb/micropython,mpalomer/micropython,adafruit/micropython,pozetroninc/micropython,swegener/micropython,oopy/micropython,deshipu/micropython,micropython/micropython-esp32,toolmacher/micropython,pozetroninc/micropython,matthewelse/micropython,toolmacher/micropython,MrSurly/micropython-esp32,henriknelson/micropython,blazewicz/micropython,hosaka/micropython,pramasoul/micropython,dinau/micropython,pramasoul/micropython,puuu/micropython,dinau/micropython,hosaka/micropython,chrisdearman/micropython,micropython/micropython-esp32,SHA2017-badge/micropython-esp32,pfalcon/micropython,swegener/micropython,toolmacher/micropython,jmarcelino/pycom-micropython,hosaka/micropython,infinnovation/micropython,blazewicz/micropython,bvernoux/micropython,tralamazza/micropython,jmarcelino/pycom-micropython,lowRISC/micropython,mpalomer/micropython,puuu/micropython,hiway/micropython,MrSurly/micropython,hiway/micropython,adafruit/micropython,chrisdearman/micropython,adafruit/circuitpython,tobbad/micropython,dmazzella/micropython,selste/micropython,turbinenreiter/micropython,trezor/micropython,dinau/micropython,lowRISC/micropython,deshipu/micropython,torwag/micropython,HenrikSolver/micropython,dxxb/micropython,blazewicz/micropython,tobbad/micropython,HenrikSolver/micropython,SHA2017-badge/micropython-esp32,ryannathans/micropython,torwag/micropython,bvernoux/micropython,bvernoux/micropython,tuc-osg/micropython,alex-march/micropython,pfalcon/micropython,mpalomer/micropython,oopy/micropython,infinnovation/micropython,MrSurly/micropython-esp32,tobbad/micropython,AriZuu/micropython,mhoffma/micropython,Timmenem/micropython,adafruit/circuitpython,swegener/micropython,TDAbboud/micropython,cwyark/micropython