scsi: ufs-qcom: change device reference clock control

As of HW major version 2, bit 'UFS_DEV_REF_CLK_EN' which is used to
gate/ungate the ref_clk to external UFS device, was moved into the
UFS register space to UFS_CFG1 register. This change adds support
to appropriately control the device reference clock and it also
adds the missing documentation for the device reference clock control
register address space.

Change-Id: I66a6a75dc5a1cf130b1cee90ae20f9f950edfb3a
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>
[subhashj@codeaurora.org: resolved trivial merge conflicts]
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
[cang@codeaurora.org: Resolved trivial merge conflicts]
Signed-off-by: Can Guo <cang@codeaurora.org>