scsi: ufs-qcom: enable hibern8 during clock gating

By default UFS link operates in FAST mode which would keep the link active
until host puts the link in hibern8. Power consumption during link active
state is huge hence it's recommended to put the link in hibern8 as soon
as possible. Clock gating mechanism kicks in after pre-defined idle timeout
(150ms at this time) shorter than the runtime suspend timeout hence it
would be idle to put the UFS link in hibern8 along with clock gating.
Note that this aggressive power management approach doesn't affect the
normal storage benchmark performance numbers as clock gating idle timeout
has been choosen to not affect storage performance benchmarks.

Change-Id: I5b88a7ea2d918750a3cc9150511e25caa1e57284
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>