uboot-imx

secure_boot: create function to determine boot mode

A function is created to detrmine if the boot mode is secure
or non-secure for differnt SoC's.

Signed-off-by: Aneesh Bansal <aneesh.bansal@nxp.com>
Acked-by: Ruchika Gupta <ruchika.gupta@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>