There are some imx8mm-based boards that contain an SN65DSI83 MIPI
DSI to LVDS bridge chip.

Add support for it so that the LVDS output can be functional by default.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>