Add support for imx8mqevk_defconfig that allows booting a mainline
kernel.
This defconfig still relies on NXP ATF and U-Boot, but in the long term
the plan is to switch to mainline ATF and U-Boot as well.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>