armv8: fsl-layerscape: Make USB masters snoopable

Program register bit of SCFG_SNPCNFGCR_USBxRDSNP and
SCFG_SNPCNFGCR_USBxWRSNP(x = 1, 2, 3) to drive USBx read/write
snoop signal on LS1043A and LS1046A.

Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>