firmware: imx: add misc svc support

Add SCU MISC SVC support which provides misc control get/set functions.

Cc: Shawn Guo <shawnguo@kernel.org>
Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>