Prior to this commit mp_hal_ticks_cpu() was not started properly. It only
started when the code was executed with a debugger attached, except for the
Teensy (i.MXRT1062) boards. As an additional fix, the CYYCNT timer is now
started at boot time.
Also rename mp_hal_ticks_cpu_init() to mp_hal_ticks_cpu_enable().
Following the code example for ESP32 of Jim Mussard.
As a side effect:
- mp_hal_ticks_cpu() was implemented,
- mp_hal_get_cpu_freq() and mp_hal_ticks_cpu_init() were added and used.
- mp_hal_pin_high() and mp_hal_pin_low() were changed for symmetry
robert-hh
Jim Mussared