drm/i2c: adv7511: Create mipi_dsi_device for ADV7533

In order to pass DSI specific parameters to the DSI host, we need the
driver to create a mipi_dsi_device that attaches to the host.

Use of_graph helpers to get the DSI host DT node. Create a dummy dsi
device using this host. Finally, attach this device to the host.

Populate few other DT parameters (number of data lanes etc) that are
required for DSI RX to work correctly. Hardcode few other parameters
(rgb, embedded_sync) for now.

Signed-off-by: Archit Taneja <architt@codeaurora.org>