fastboot: Move fastboot response functions to fastboot core

The functions and a few define to generate a fastboot message to be sent
back to the host were so far duplicated among the users.

Move them all to a common place.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
5 files changed