drm/msm/dsi-staging: Set the dsi panel type

Parse the DTS panel type settings. Consider the default
panel physical type as LCD. We need to set OLED in DTS if
the panel is an OLED type.

Change-Id: Ib53651ab3861e75bf061f38d60a2f6135c1f537d
Signed-off-by: Yuan Zhao <yzhao@codeaurora.org>