[SCSI] ufs: add operation for the uic power mode change

Setting PA_PWRMode using DME_SET triggers the power mode
change. And then the result will be given by the HCS.UPMCRS.
This operation should be done atomically.

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Tested-by: Yaniv Gardi <ygardi@codeaurora.org>
Signed-off-by: Santosh Y <santoshsy@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>