scsi: ufs: gate ref_clk during aggressive clk gating

The clock gating work has been moved to using hrtimer based
delay guaranteeing hibern8 to finish before we gate the clocks.
This allows us to gate the ref clock along with other ufs clocks
during aggressive clock gating. The latencies involved in voting/
devoting ref clk is acceptable and helps in saving more power.

Change-Id: I92b86fad25041311d00fbfc58b3d5620ade7ee38
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>