dt-bindings: display: renesas: Add R-Car M3-N HDMI TX DT bindings

The M3-N HDMI TX controller is compatible with the M3-W and H3. No
extension to the DT bindings are needed.

Add an SoC-specific compatible string in case differences between the IP
versions are found later and require model-specific handling.
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

Documentation/devicetree/bindings/display/bridge/renesas,dw-hdmi.txt

@@ -14,6 +14,7 @@ Required properties:
 - compatible : Shall contain one or more of
   - "renesas,r8a7795-hdmi" for R8A7795 (R-Car H3) compatible HDMI TX
   - "renesas,r8a7796-hdmi" for R8A7796 (R-Car M3-W) compatible HDMI TX
+  - "renesas,r8a77965-hdmi" for R8A77965 (R-Car M3-N) compatible HDMI TX
   - "renesas,rcar-gen3-hdmi" for the generic R-Car Gen3 compatible HDMI TX
 
     When compatible with generic versions, nodes must list the SoC-specific