arm64: dts: renesas: ulcb: Rename EtherAVB "mdc" pin group to "mdio"

On other Renesas SoCs, the pin group for the MDIO bus is named "mdio"
instead of "mdc".  Fix the inconsistency, now the pinctrl drivers for
R-Car H3, M3-W, and M3-N have gained support for the traditional pin
group name.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/ulcb.dtsi

@@ -255,12 +255,12 @@ &pfc {
 
 	avb_pins: avb {
 		mux {
-			groups = "avb_link", "avb_mdc", "avb_mii";
+			groups = "avb_link", "avb_mdio", "avb_mii";
 			function = "avb";
 		};
 
-		pins_mdc {
-			groups = "avb_mdc";
+		pins_mdio {
+			groups = "avb_mdio";
 			drive-strength = <24>;
 		};