scsi: ufs: gate ref_clk during aggressive clk gating

Gate ref clock along with other ufs clocks during aggressive
clock gating. The latencies involved in voting/devoting ref clk
is acceptable. This will allow faster XO shutdown instead of
gating off the clock during 3s idle runtime suspend.

Change-Id: I6e160f62f3600adf28997d5bb2868d1924208d42
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>