scsi: ufs-msm: inform PHY about analog rails power down

UFS PHY analog rails (VDDA_PHY_0P9 & VDDA_PLL_1P8) can be power collapsed
while the UFS link is in hibern8 state but PHY needs to be informed about
the power collapse by writing 0 to its power down control register. If PHY
is not informed about it, hibern8 exit might fail. This fixes this problem.

Change-Id: If897681569ca0073f2075acf8a9014da8d762827
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>