arm64: dts: msm8916: Add display support

The MSM8916 SoC contains a MDP5 based display block, and one DSI output.
Add the top level MDSS DT node, and the MDP5, DSI and DSI PHY children
sub-blocks. Establish the link between MDP5's INTF1 output port and DSI's
input port.

Cc: Andy Gross <andy.gross@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>