board: dragonboard410c: Drop UNSTUFF_BITS() macro

board: dragonboard410c: Drop UNSTUFF_BITS() macro

This was originally taken from Linux, but at this point it's an inline
function upstream and no longer a macro. Given that we just want to extract
the serial number from the MMC CID, let's just inline that specifically.
This is also the style used in the MMC core code within U-Boot.

Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by:
Link: https://lore.kernel.org/r/20250407-db410c-fixes-v1-4-524aefbc8bb4@linaro.org
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>