mfd: rtsx: Configure to enter a deeper power-saving mode in S3

Set a bit to enable rts5227 and rts5249 to enter a deeper internal
power-saving mode in S3, and recover it after resuming.

Signed-off-by: Wei WANG <wei_wang@realsil.com.cn>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>