ARM: dts: msm: enable MPP4 invert on 8996

Enable MPP4 by default at boot-up which enables HDMI 5V.
This is needed for continuous splash screen to make sure
5V is not turned off when booting into kernel.

Change-Id: Ibbce17bb85d82cca42c0bcf0f53fadecace103fb
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>