ARM64: dts: meson-gxm: add GXM specific USB host configuration

The USB configuration on GXM is slightly different than on GXL. The dwc3
controller's internal hub has three USB2 ports (instead of 2 on GXL)
along with a dedicated USB2 PHY for this port. However, it seems that
there are no pins on GXM which would allow connecting the third port to
a physical USB port.
Passing the third PHY is required though, because without it none of the
other USB ports is working (this seems to be a limitation of how the
internal USB hub works, if one PHY is disabled then no USB port works).

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxm.dtsi

@@ -80,6 +80,19 @@
 	};
 };
 
+&apb {
+	usb2_phy2: phy@78040 {
+		compatible = "amlogic,meson-gxl-usb2-phy";
+		#phy-cells = <0>;
+		reg = <0x0 0x78040 0x0 0x20>;
+		clocks = <&clkc CLKID_USB>;
+		clock-names = "phy";
+		resets = <&reset RESET_USB_OTG>;
+		reset-names = "phy";
+		status = "okay";
+	};
+};
+
 &clkc_AO {
 	compatible = "amlogic,meson-gxm-aoclkc", "amlogic,meson-gx-aoclkc";
 };
@@ -100,3 +113,7 @@
 &hdmi_tx {
 	compatible = "amlogic,meson-gxm-dw-hdmi", "amlogic,meson-gx-dw-hdmi";
 };
+
+&dwc3 {
+	phys = <&usb3_phy>, <&usb2_phy0>, <&usb2_phy1>, <&usb2_phy2>;
+};