armv8: fsl-layerscape: Support loading PPA header from eMMC/SD and NAND Flash

Add Kconfig option to support loading PPA header from eMMC/SD and
NAND Flash.

Signed-off-by: Sumit Garg <sumit.garg@nxp.com>
Signed-off-by: Udit Agarwal <udit.agarwal@nxp.com>
Tested-by: Vinitha Pillai <vinitha.pillai@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>