scsi: ufs: introduce hibern8_notify callback

Some UFS host controller may need to configure some things around
hibern8 enter/exit

Signed-off-by: Kiwoong Kim <kwmad.kim@samsung.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>