py/mkrules.cmake: Rename QSTR_DEFS variables to QSTRDEFS.
py/mkrules.cmake: Rename QSTR_DEFS variables to QSTRDEFS.

And also MICROPY_PY_QSTRDEFS to MICROPY_QSTRDEFS_PY.  These variables are
all related.

Signed-off-by: Damien George <99e6b749acbfbe2a596df99e91d24d6e1fdbee00@micropython.org>

henriknelson/micropython,bvernoux/micropython,bvernoux/micropython,henriknelson/micropython,adafruit/circuitpython,bvernoux/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,henriknelson/micropython,bvernoux/micropython,adafruit/circuitpython,henriknelson/micropython,adafruit/circuitpython,henriknelson/micropython,bvernoux/micropython