scsi: ufs-qcom: phy/hcd: Refactoring phy clock handling

Add phy clock enable code to phy_power_on/off callbacks, and
remove explicit calls to enable these phy clocks from the
ufs-qcom hcd driver.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>