Initial broadcom port for Raspberry Pi

[tannewt]

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

[tannewt]

These are temporary USB PIDs under the Raspberry Pi VID. I'm waiting to hear from @ghollingworth about the official values.

[dhalbert]

Amazing work! Lots of good cleanup removing 32-bit assumptions.

[tannewt]

Ok, I've pushed a new version. It includes I2C support too.

[dhalbert]

Thanks for the updates, and hurrah for I2C! zero2w port is failing for some compilation reason, but the pi4b is working.

[dhalbert]

Thanks for the updates, and hurrah for I2C! zero2w port is failing for some compilation reason, but the pi4b is working.

Looks like a simple fix: I added a #include. If this works I will merge.

[dhalbert]

@tannewt Making a commit from the GitHub web interface seems to have upset the build cloning optimizations you added. (EDIT: MAYBE NOT) From https://github.com/adafruit/circuitpython/runs/4313459204?check_suite_focus=true:

Run git describe --dirty --tags
  git describe --dirty --tags
  echo >>$GITHUB_ENV CP_VERSION=$(git describe --dirty --tags)
  shell: /usr/bin/bash -e {0}
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.8.12/x64
fatal: No tags can describe 'e98223cbae0c9dfe636badcc49bb85fa3f905cfa'.
Try --always, or create some tags.
Error: Process completed with exit code 128.

[dhalbert]

@tannewt I pushed an empty commit from your repo, and it didn't fix the problem. Hmm.