py/qstr: Rewrite find_qstr to make manifest that it returns a valid ptr.
py/qstr: Rewrite find_qstr to make manifest that it returns a valid ptr.

So long as the input qstr identifier is valid (below the maximum number of
qstrs) the function will always return a valid pointer.  This patch
eliminates the "return 0" dead-code.

MrSurly/micropython,pramasoul/micropython,pfalcon/micropython,henriknelson/micropython,tobbad/micropython,blazewicz/micropython,pfalcon/micropython,pramasoul/micropython,trezor/micropython,blazewicz/micropython,infinnovation/micropython,tralamazza/micropython,swegener/micropython,dmazzella/micropython,tralamazza/micropython,adafruit/circuitpython,selste/micropython,selste/micropython,lowRISC/micropython,blazewicz/micropython,trezor/micropython,ryannathans/micropython,bvernoux/micropython,selste/micropython,blazewicz/micropython,swegener/micropython,trezor/micropython,pozetroninc/micropython,ryannathans/micropython,selste/micropython,kerneltask/micropython,adafruit/circuitpython,adafruit/circuitpython,MrSurly/micropython,adafruit/micropython,infinnovation/micropython,infinnovation/micropython,dmazzella/micropython,bvernoux/micropython,MrSurly/micropython,pozetroninc/micropython,blazewicz/micropython,kerneltask/micropython,swegener/micropython,lowRISC/micropython,swegener/micropython,pfalcon/micropython,ryannathans/micropython,tobbad/micropython,dmazzella/micropython,tobbad/micropython,lowRISC/micropython,adafruit/circuitpython,henriknelson/micropython,infinnovation/micropython,pramasoul/micropython,adafruit/micropython,bvernoux/micropython,trezor/micropython,adafruit/micropython,MrSurly/micropython,ryannathans/micropython,kerneltask/micropython,pramasoul/micropython,henriknelson/micropython,pozetroninc/micropython,bvernoux/micropython,bvernoux/micropython,dmazzella/micropython,lowRISC/micropython,selste/micropython,henriknelson/micropython,infinnovation/micropython,tobbad/micropython,henriknelson/micropython,pozetroninc/micropython,tobbad/micropython,adafruit/micropython,adafruit/micropython,trezor/micropython,pramasoul/micropython,pfalcon/micropython,adafruit/circuitpython,kerneltask/micropython,MrSurly/micropython,lowRISC/micropython,swegener/micropython,tralamazza/micropython,pozetroninc/micropython,pfalcon/micropython,adafruit/circuitpython,tralamazza/micropython,ryannathans/micropython,kerneltask/micropython