scsi: ufs-qcom: Control ufs-ref-clk-supply from host node

UFS device requires a reference clock for
operating in HS (High-speed) gears. This device
reference clock is provided by the dedicated SoC pad
on QCOM platforms. This rail needs to be powered by
1.2v power pads.
Currently, that supply is being controlled
in the ufs phy driver. Phy driver doesn't have any
knowledge of the system-pm state. Hence, it can't
selectively toggle this supply.

Hence, move the control of this supply to ufs driver.
The host driver has the knowledge of system-pm state &
is better equipped to toggle this supply.

Change-Id: Ia19c6e7d9ffb856a01d31ab56ea97a7bb1affae6
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
[cang@codeaurora.org: resolved trivial merge conflicts]
Signed-off-by: Can Guo <cang@codeaurora.org>