ARM: tegra: nexus7: Enable USB OTG mode

Nexus 7 has OTG-cable microUSB port, enable OTG mode. USB peripheral
devices now can be connected to Nexus 7 using OTG adapter, switching
USB port into host mode.

Signed-off-by: Dmitry Osipenko <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

arch/arm/boot/dts/tegra30-asus-nexus7-grouper-common.dtsi

···
 			interrupts = <TEGRA_GPIO(V, 1) IRQ_TYPE_EDGE_BOTH>;
 
 			summit,enable-charge-control = <SMB3XX_CHG_ENABLE_PIN_ACTIVE_LOW>;
+			summit,inok-polarity = <SMB3XX_SYSOK_INOK_ACTIVE_LOW>;
 			summit,enable-usb-charging;
 
 			monitored-battery = <&battery_cell>;
+
+			usb_vbus: usb-vbus {
+				regulator-name = "usb_vbus";
+				regulator-min-microvolt = <5000000>;
+				regulator-max-microvolt = <5000000>;
+				regulator-min-microamp = <750000>;
+				regulator-max-microamp = <750000>;
+
+				/*
+				 * SMB347 INOK input pin is connected to PMIC's
+				 * ACOK output, which is fixed to ACTIVE_LOW as
+				 * long as battery voltage is in a good range.
+				 *
+				 * Active INOK disables SMB347 output, so polarity
+				 * needs to be toggled when we want to get the
+				 * output.
+				 */
+				summit,needs-inok-toggle;
+			};
 		};
 	};
 
···
 	usb@7d000000 {
 		compatible = "nvidia,tegra30-udc";
 		status = "okay";
-		dr_mode = "peripheral";
+		dr_mode = "otg";
+		vbus-supply = <&usb_vbus>;
 	};
 
 	usb-phy@7d000000 {
 		status = "okay";
-		dr_mode = "peripheral";
+		dr_mode = "otg";
 		nvidia,hssync-start-delay = <0>;
 		nvidia,xcvr-lsfslew = <2>;
 		nvidia,xcvr-lsrslew = <2>;