ARM: dts: msm: Add UFS's Vccq2 voltage level in DT file

This change allows selecting the UFS Vccq2 voltage level by setting the
UFS's entry vccq2-voltage-level in the device tree.
If UFS's Vccq2 voltage level setting is not found in the device tree,
use default values provided by the driver.

Change-Id: I9e889e7889ee50c4dcd964f507b39500d10f646c