msm: mdss: Request for TE GPIO only for command mode panel

There is a possibility that a board has TE GPIO in dts file and we
request and use it in video mode also. Hence, request and enable the
TE GPIO only when panel is in command mode.

Change-Id: I89b9b89f569f341940d2b0471fc8bea0345dffb6
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>