arm/dt: msm8974: Add HDMI MUX gpios support for LiQUID8974

Set pm8841 MPP3 for digital output active-high.
This selection signal must be configured to 1.8V.
Use pm8841 VIN2 as VIN supply as it is mapped to S3A.

Set pm8841 MPP4 for digital output active-high, since it is
connected to the HDMI_MUX_EN pin on the TS3DV621 HDMI MUX.
This enable signal must be configured to VPH_PWR.
Use pm8841 VIN0 as VIN supply as it is mapped to VPH (PVDD).

Change-Id: Ib47f03e2c5569f40f52c657057cd77479e7e6685
Signed-off-by: Eugene Yasman <eyasman@codeaurora.org>
Signed-off-by: Asaf Penso <apenso@codeaurora.org>