scsi: ufs-qcom: disable the UFS PHY reference clock during clock gating

If UFS link is inactive then UFS PHY reference clock can be switched off
to save power. As of now, this clock is turned off only during the suspend
(runtime and system). This change extend support to turn off the PHY
reference clock during clock gating (after pre-defined idle timeout) as
well.

Change-Id: Id1f83a003e228abedf222157691998470c3f7932
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>