py/asmarm: Use __builtin___clear_cache instead of __clear_cache.
py/asmarm: Use __builtin___clear_cache instead of __clear_cache.

__clear_cache causes a compile error when using clang.  Instead use
__builtin___clear_cache which is available under both gcc and clang.

Also replace tabs with spaces in this section of code (introduced by a
previous commit).

henriknelson/micropython,selste/micropython,pramasoul/micropython,selste/micropython,pramasoul/micropython,pfalcon/micropython,tobbad/micropython,bvernoux/micropython,pozetroninc/micropython,pozetroninc/micropython,adafruit/circuitpython,pramasoul/micropython,kerneltask/micropython,pfalcon/micropython,bvernoux/micropython,MrSurly/micropython,tobbad/micropython,henriknelson/micropython,pramasoul/micropython,pozetroninc/micropython,pozetroninc/micropython,tobbad/micropython,bvernoux/micropython,tobbad/micropython,tobbad/micropython,henriknelson/micropython,trezor/micropython,henriknelson/micropython,adafruit/circuitpython,selste/micropython,kerneltask/micropython,bvernoux/micropython,pfalcon/micropython,kerneltask/micropython,kerneltask/micropython,selste/micropython,MrSurly/micropython,adafruit/circuitpython,pfalcon/micropython,kerneltask/micropython,trezor/micropython,bvernoux/micropython,MrSurly/micropython,adafruit/circuitpython,henriknelson/micropython,adafruit/circuitpython,trezor/micropython,pfalcon/micropython,pozetroninc/micropython,pramasoul/micropython,trezor/micropython,MrSurly/micropython,selste/micropython,MrSurly/micropython,adafruit/circuitpython,trezor/micropython