sw: enable greybus app in FW release directory

Hi @jadonk , Tested the greybus-mikrobus application with BCF Rev C5, this PR needs to be merged for the on-board sensors to work properly as they are behind the analog switch. https://github.com/jadonk/greybus-for-zephyr/pull/4 and also greybus-for-zephyr-mikrobus submodule need to be updated

Logs for testing has been added here: https://github.com/jadonk/greybus-for-zephyr/pull/4#issuecomment-991946977