ARM: at91/dt: enable the RTT block on the at91sam9m10g45ek board

Enable the RTT and GPBR devices and specify the general purpose register
used to store the current time.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91sam9m10g45ek.dts

@@ -161,6 +161,15 @@ pwm0: pwm@fffb8000 {
 				pinctrl-0 = <&pinctrl_pwm_leds>;
 			};
 
+			rtc@fffffd20 {
+				atmel,rtt-rtc-time-reg = <&gpbr 0x0>;
+				status = "okay";
+			};
+
+			gpbr: syscon@fffffd60 {
+				status = "okay";
+			};
+
 			rtc@fffffdb0 {
 				status = "okay";
 			};