drm/msm/dsi-staging: add dsi cmd/vid mode to display info

Need the ability to communicate which modes the DSI panel is
operating capable of operating in, command or video mode.

Change-Id: I44a5f01c7dad4af6a14590fdbf2349b675f65393
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>