phy-qcom-ufs-qmp-v3 supports SVS2 voltage scaling mode that
allows lowest power consumption in HS G1. The PHY must be put
in hibern8 state before configuring the PHY to enter SVS2 mode.
The voltage can be reduced after this to SVS2 level.
This change exposes an API that allows the UFS driver to
configure the PHY to enter SVS2 mode.
Change-Id: I2ef01d98603840289c436e14bf3df54a2ab9198b
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>