rockchip: rk3288-firefly: Add gmac definition

Add a definition for the gmac interface to the firefly device-tree.
Copied verbatim from the linux kernel.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Acked-by: Simon Glass <sjg@chromium.org>

arch/arm/dts/rk3288-firefly.dtsi

@@ -146,6 +146,22 @@
 	status = "okay";
 };
 
+&gmac {
+	assigned-clocks = <&cru SCLK_MAC>;
+	assigned-clock-parents = <&ext_gmac>;
+	clock_in_out = "input";
+	pinctrl-names = "default";
+	pinctrl-0 = <&rgmii_pins>, <&phy_rst>, <&phy_pmeb>, <&phy_int>;
+	phy-supply = <&vcc_lan>;
+	phy-mode = "rgmii";
+	snps,reset-active-low;
+	snps,reset-delays-us = <0 10000 1000000>;
+	snps,reset-gpio = <&gpio4 8 GPIO_ACTIVE_LOW>;
+	tx_delay = <0x30>;
+	rx_delay = <0x10>;
+	status = "okay";
+};
+
 &hdmi {
 	ddc-i2c-bus = <&i2c5>;
 	status = "okay";