armv8: fsl-layerscape: Consolidate the LSCH2 common defines

Both LS1012A and LS1043A belong to FSL_LSCH2 and share some common
configurations. So put the common define under FSL_LSCH2 to increase
readability.

Signed-off-by: Gong Qianyu <Qianyu.Gong@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>