py/builtinimport: Remove unreachable code for relative imports.
py/builtinimport: Remove unreachable code for relative imports.

The while-loop that calls chop_component will guarantee that level==-1 at
the end of the loop.  Hence the code following it is unnecessary.

The check for p==this_name will catch imports that are beyond the
top-level, and also covers the case of new_mod_q==MP_QSTR_ (equivalent to
new_mod_l==0) so that check is removed.

There is also a new check at the start for level>=0 to guard against
__import__ being called with bad level values.

AriZuu/micropython,oopy/micropython,alex-robbins/micropython,adafruit/circuitpython,oopy/micropython,bvernoux/micropython,AriZuu/micropython,MrSurly/micropython-esp32,blazewicz/micropython,PappaPeppar/micropython,tobbad/micropython,bvernoux/micropython,bvernoux/micropython,pramasoul/micropython,MrSurly/micropython,chrisdearman/micropython,selste/micropython,tobbad/micropython,alex-robbins/micropython,infinnovation/micropython,MrSurly/micropython,MrSurly/micropython-esp32,trezor/micropython,TDAbboud/micropython,pozetroninc/micropython,chrisdearman/micropython,AriZuu/micropython,micropython/micropython-esp32,lowRISC/micropython,MrSurly/micropython,pfalcon/micropython,alex-robbins/micropython,adafruit/circuitpython,henriknelson/micropython,SHA2017-badge/micropython-esp32,chrisdearman/micropython,SHA2017-badge/micropython-esp32,blazewicz/micropython,trezor/micropython,pozetroninc/micropython,lowRISC/micropython,dmazzella/micropython,trezor/micropython,MrSurly/micropython-esp32,swegener/micropython,alex-robbins/micropython,PappaPeppar/micropython,alex-robbins/micropython,pfalcon/micropython,adafruit/micropython,pozetroninc/micropython,lowRISC/micropython,dmazzella/micropython,swegener/micropython,chrisdearman/micropython,PappaPeppar/micropython,infinnovation/micropython,deshipu/micropython,micropython/micropython-esp32,Timmenem/micropython,swegener/micropython,swegener/micropython,henriknelson/micropython,Timmenem/micropython,AriZuu/micropython,ryannathans/micropython,ryannathans/micropython,Timmenem/micropython,lowRISC/micropython,pfalcon/micropython,bvernoux/micropython,TDAbboud/micropython,MrSurly/micropython-esp32,adafruit/circuitpython,adafruit/circuitpython,trezor/micropython,tralamazza/micropython,deshipu/micropython,pramasoul/micropython,micropython/micropython-esp32,tralamazza/micropython,tralamazza/micropython,tobbad/micropython,adafruit/micropython,MrSurly/micropython,deshipu/micropython,swegener/micropython,HenrikSolver/micropython,TDAbboud/micropython,henriknelson/micropython,MrSurly/micropython,Timmenem/micropython,blazewicz/micropython,infinnovation/micropython,tralamazza/micropython,dmazzella/micropython,lowRISC/micropython,torwag/micropython,selste/micropython,kerneltask/micropython,adafruit/circuitpython,pramasoul/micropython,PappaPeppar/micropython,selste/micropython,ryannathans/micropython,micropython/micropython-esp32,kerneltask/micropython,torwag/micropython,kerneltask/micropython,dmazzella/micropython,adafruit/micropython,pramasoul/micropython,trezor/micropython,HenrikSolver/micropython,SHA2017-badge/micropython-esp32,oopy/micropython,ryannathans/micropython,torwag/micropython,infinnovation/micropython,selste/micropython,TDAbboud/micropython,deshipu/micropython,TDAbboud/micropython,henriknelson/micropython,oopy/micropython,blazewicz/micropython,selste/micropython,adafruit/micropython,AriZuu/micropython,tobbad/micropython,PappaPeppar/micropython,tobbad/micropython,oopy/micropython,infinnovation/micropython,micropython/micropython-esp32,adafruit/micropython,pfalcon/micropython,HenrikSolver/micropython,pfalcon/micropython,MrSurly/micropython-esp32,torwag/micropython,kerneltask/micropython,adafruit/circuitpython,SHA2017-badge/micropython-esp32,pozetroninc/micropython,henriknelson/micropython,pramasoul/micropython,chrisdearman/micropython,kerneltask/micropython,bvernoux/micropython,torwag/micropython,Timmenem/micropython,HenrikSolver/micropython,HenrikSolver/micropython,blazewicz/micropython,pozetroninc/micropython,ryannathans/micropython,deshipu/micropython,SHA2017-badge/micropython-esp32