build: run compliance checks

[cfriedt]

Zephyr has some scripts that check various compliance items (the compliance items are selectable). This will catch things like missing copyright notices but it can be configured to catch virtually every issue.

It might be worth it to skip subsys/greybus/*.c but to check subsys/greybus/platform/ because much of the original NuttX code will likely not adhere to the same styles that Zephyr uses. A not necessarily obvious goal is to also leave much of the original NuttX / Greybus code intact as-is with as little change as possible.

https://github.com/zephyrproject-rtos/zephyr/blob/master/.github/workflows/compliance.yml