imx-mkimage: new package

This package add support for imx-mkimage for iMX8M.
Currently the only hardware it's tested for.

Signed-off-by: Erik Larsson <karl.erik.larsson@gmail.com>
Signed-off-by: Christopher Dahlberg <crille.dahlberg@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>