ARM: dts: msm: Enable RM69090 truly cmd mode panel support

Add changes to:
    1.add ldos for dsi and panel,configure PMIC gpio 12 as a fixed
    regulator and add it as panel power supply.
    2.add panel properties for RM69090 truly command mode panel.

Change-Id: I7c035bc4cd99f443373a4d5bc30df964146f68de
Signed-off-by: Xipeng Gu <guxipeng@codeaurora.org>