scsi: ufs: add UFS device reset support

Some platforms may have a SOC pin/gpio connected to UFS device's
RST_n to allow the UFS device reset. This change adds support to
trigger device reset on such platforms.

Change-Id: Ie4faa47fb76837dba909f9a3d0dfe11bc69659e1
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
[cang@codeaurora.org: resolved trivial merge conflicts]
Signed-off-by: Can Guo <cang@codeaurora.org>