uboot-imx

SECURE_BOOT: Use default bootargs

For secure boot, currently we were using fixed bootargs for all SoCs.
This is not needed and we can use the bootargs which are used in
non-secure boot.

Signed-off-by: Aneesh Bansal <aneesh.bansal@nxp.com>
Signed-off-by: Saksham Jain <saksham.jain@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>