arm64: dts: imx8mq-librem5-devkit: Enable the LCD panel

Enable LCD panel output by adding nodes for the NWL DSI host controller,
the Rocktech panel and the eLCDIF display controller.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>