arm64: dts: ulcb: Set drive-strength for ravb pins

The EthernetAVB should not depend on the bootloader to setup correct
drive-strength values.  Values for drive-strength where found by
examining the registers after the bootloader has configured the
registers and successfully used the EthernetAVB.

Based on:
* commit 7d73a4da ("arm64: dts: r8a7795: salvator-x: Set drive-strength
  for ravb pins")
* commit 4903987033be ("arm64: dts: r8a7796: salvator-x: Set drive-strength
  for ravb pins")

Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

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

@@ -198,8 +198,22 @@ &pfc {
 	pinctrl-names = "default";
 
 	avb_pins: avb {
-		groups = "avb_mdc";
-		function = "avb";
+		mux {
+			groups = "avb_link", "avb_phy_int", "avb_mdc",
+				 "avb_mii";
+			function = "avb";
+		};
+
+		pins_mdc {
+			groups = "avb_mdc";
+			drive-strength = <24>;
+		};
+
+		pins_mii_tx {
+			pins = "PIN_AVB_TX_CTL", "PIN_AVB_TXC", "PIN_AVB_TD0",
+			       "PIN_AVB_TD1", "PIN_AVB_TD2", "PIN_AVB_TD3";
+			drive-strength = <12>;
+		};
 	};
 
 	i2c2_pins: i2c2 {