Arm: dts: Primary disp perf for msm8x10

Add primary display interface preference property
to mdss-mdp device node. This allows MDP to inform
each controller if it is confirgured as the preferred
primary panel interface. Move the panel devices under
the mdss-mdp device node from soc since panels will
no longer be considered a device. This change is required
to implement panel detection mechanism. Update mdss node
with 8x10 plaform specific GPIO and regulator settings.

Change-Id: I46687673f858d89d50aa5fa11bb2831acaf44ada
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>