scsi: ufs: add support for low voltage VCC support

Both UFS3.0 and higher version of ufs device are capable of running
at lower level (2.5v) of VCC rail. If both host and device supports
2.5v level then we do runtime switch of UFS VCC voltage level.

Change-Id: I6fea6c354cde5f7bd9d2a8a275c66e842726d358
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Nitin Rawat <nitirawa@codeaurora.org>