devicetree/bindings: display: Add bindings for two Mitsubishi panels

The AA104XD12 and AA121TD01 are LVDS display panels. Their bindings are
modelled on the the LVDS panel bindings.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Rob Herring <robh@kernel.org>