scsi: ufs: call clk_scale_notify only if clocks are scaled

Currently vendor specific callback clk_scale_notify() is called even
if clock scaling state is not changed, this change optimizes it.

Change-Id: I5887effa43c957cc4fe434a239419353204de6d3
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>