of: Add MIPI DSI bus device tree bindings

Document the device tree bindings for the MIPI DSI bus. The MIPI Display
Serial Interface specifies a serial bus and a protocol for communication
between a host and up to four peripherals.

Signed-off-by: Thierry Reding <treding@nvidia.com>

diff --cc Documentation/devicetree/bindings/mipi/dsi/mipi-dsi-bus.txt
Simple merge