With public declarations moved to extmod/modmachine.h. It's now mandatory
for a port to define MICROPY_PY_MACHINE_PWM_INCLUDEFILE if it enables
MICROPY_PY_MACHINE_PWM. This follows how extmod/machine_wdt.c works.
All ports have been updated to work with this modified scheme.
Signed-off-by: Damien George <damien@micropython.org>
7e7af71527