ARM: dts: r8a7779: marzen: Configure pinmuxing for the DU0 input clock

DU0 uses an externally provided clock, but the corresponding pin isn't
correctly muxed. Fix it.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7779-marzen.dts

@@ -170,7 +170,7 @@ &pfc {
 
 	du_pins: du {
 		du0 {
-			groups = "du0_rgb888", "du0_sync_1", "du0_clk_out_0";
+			groups = "du0_rgb888", "du0_sync_1", "du0_clk_out_0", "du0_clk_in";
 			function = "du0";
 		};
 		du1 {