ARM: tegra: colibri_t20: annotate usb ehci instances

Annotate USB EHCI instances.
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm/boot/dts/tegra20-colibri-iris.dts

@@ -83,6 +83,7 @@ i2c_ddc: i2c@7000c400 {
 		status = "okay";
 	};
 
+	/* EHCI instance 0: USB1_DP/N -> USBC_P/N */
 	usb@c5000000 {
 		status = "okay";
 	};
@@ -92,6 +93,7 @@ usb-phy@c5000000 {
 		vbus-supply = <&reg_usbc_vbus>;
 	};
 
+	/* EHCI instance 2: USB3_DP/N -> USBH_P/N */
 	usb@c5008000 {
 		status = "okay";
 	};

arch/arm/boot/dts/tegra20-colibri.dtsi

@@ -454,6 +454,7 @@ emc-table@333000 {
 		};
 	};
 
+	/* EHCI instance 1: ULPI PHY -> AX88772B (On-module) */
 	usb@c5004000 {
 		status = "okay";
 		nvidia,phy-reset-gpio = <&gpio TEGRA_GPIO(V, 1)