ARM: dts: msm: Add UFS's Vcc voltage level entry for SDM845

Allows selecting the UFS's Vcc voltage level via the device tree setting.
If the device tree does not specify the UFS's vcc-voltage-level,
the default values specified in the code will be used.

Change-Id: I94d69a084bfd8719d3e08512174ef319ddc53704
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>