ARM: dts: aspeed: Add RTC node

The ASPEED ast2400 and ast2500 both contain an on board RTC device.
Signed-off-by: Joel Stanley <joel@jms.id.au>

arch/arm/boot/dts/aspeed-g4.dtsi

@@ -209,6 +209,12 @@ timer: timer@1e782000 {
 				clock-names = "PCLK";
 			};
 
+			rtc: rtc@1e781000 {
+				compatible = "aspeed,ast2400-rtc";
+				reg = <0x1e781000 0x18>;
+				status = "disabled";
+			};
+
 			uart1: serial@1e783000 {
 				compatible = "ns16550a";
 				reg = <0x1e783000 0x20>;

arch/arm/boot/dts/aspeed-g5.dtsi

@@ -274,6 +274,12 @@ gpio: gpio@1e780000 {
 				#interrupt-cells = <2>;
 			};
 
+			rtc: rtc@1e781000 {
+				compatible = "aspeed,ast2500-rtc";
+				reg = <0x1e781000 0x18>;
+				status = "disabled";
+			};
+
 			timer: timer@1e782000 {
 				/* This timer is a Faraday FTTMR010 derivative */
 				compatible = "aspeed,ast2400-timer";