msm: mdss: Support panel mode selection through GPIO

Some panel supports video mode and command mode selection
through GPIO pin state. These dtsi entries allow to
configure such panel mode. GPIO high or low value
can be associated with any mode of panel.

Change-Id: Idf073279e2f039fa07ad2449a327eab14a0142c7
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>