armv8: Make SEC read/write as snoopable for LS1043

For LS1043, SEC read/writes are made snoopable by setting
the corresponding bits in SCFG to avoid coherency issues.

Signed-off-by: Aneesh Bansal <aneesh.bansal@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>