ARM: at91: usb_a9g20 add DT i2c support

Use i2c-gpio and enable rv3029 RTC.

Enable the rtc in the sam9g20 defconfig.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/boot/dts/usb_a9g20.dts b/arch/arm/boot/dts/usb_a9g20.dts
index 71d83ef..0ea90b5 100644
--- a/arch/arm/boot/dts/usb_a9g20.dts
+++ b/arch/arm/boot/dts/usb_a9g20.dts
@@ -97,4 +97,13 @@
 			gpio-key,wakeup;
 		};
 	};
+
+	i2c@0 {
+		status = "okay";
+
+		rv3029c2@56 {
+			compatible = "rv3029c2";
+			reg = <0x56>;
+		};
+	};
 };