ARM: dts: Fix backlight issue for QVGA AUO command mode panel

AUO panel supports DCS backlight control interface. Updated
mdss-dsi-bl-pmic-control-type property accordingly.

Change-Id: I60eecddc66d3d65ef4f5c7295a55b8ae7725b557
Signed-off-by: Sachin Bhayare <sachin.bhayare@codeaurora.org>