scsi: ufs: add shutdown support

This patch adds the UFS device/link shutdown support when system goes to
shutdown. During shutdown, UFS device & link would be put in power off
state.

Change-Id: I4ec31d62b69182495ff6d6b07505651937d37385
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>