scsi: ufs-qcom: don't disable host PHY ref_clk during aggressive gating

Enabling & disabling host PHY ref_clk generally may have high latencies
hence don't disable them during aggresive clock gating otherwise it could
affect the UFS performance badly.

Change-Id: I1741c75a6295c7c0b0d77ff578ab977213dcc484
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>