The ``reset`` and ``read`` pins should be optional, but the espressif
code had several places where it assumed they are not, and a bug that
caused a crash on ``release_displays`` if they were made optional.
The bug was caused by the fields for storing pin numbers being set
to ``NO_PIN``, which has value of -1, while the fields have type
``uint8_t``. That set the actual value to 255, and a subsequent
comparison to ``NO_PIN`` returned false.
This targets the 64-bit CPU Raspberry Pis. The BCM2711 on the Pi 4
and the BCM2837 on the Pi 3 and Zero 2W. There are 64-bit fixes
outside of the ports directory for it.
There are a couple other cleanups that were incidental:
* Use const mcu_pin_obj_t instead of omitting the const. The structs
themselves are const because they are in ROM.
* Use PTR <-> OBJ conversions in more places. They were found when
mp_obj_t was set to an integer type rather than pointer.
* Optimize submodule checkout because the Pi submodules are heavy
and unnecessary for the vast majority of builds.
Fixes#4314
