armv8: fsl-layerscape: Add support for efi_loader RTS reset

When implementing efi loader support, we can expose runtime services
for payloads. One such service is CPU reset.

This patch implements RTS CPU reset support for layerscape systems.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: York Sun <york.sun@nxp.com>