dt-bindings: display: renesas: Add r8a774b1 support

Document RZ/G2N (R8A774B1) SoC bindings.
Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

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

@@ -13,6 +13,7 @@ Required properties:
 
 - compatible : Shall contain one or more of
   - "renesas,r8a774a1-hdmi" for R8A774A1 (RZ/G2M) compatible HDMI TX
+  - "renesas,r8a774b1-hdmi" for R8A774B1 (RZ/G2N) compatible HDMI TX
   - "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