Add DSI and panel nodes to get graphics up and running
on the Nexus7.

This still depends on the panel driver being present
along with the rpmclk code.

Feedback would be greatly appreciated!

Cc: Archit Taneja <architt@codeaurora.org>
Cc: vinay simha <vinaysimha@inforcecomputing.com>
Cc: andy.gross@linaro.org
Cc: robdclark@gmail.com
Cc: linux-arm-msm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>