ARM: dts: mxs: enable rtc for imx23 and imx28

Enable rtc for imx23 and imx28.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx23.dtsi

@@ -289,8 +289,9 @@
 			};
 
 			rtc@8005c000 {
+				compatible = "fsl,imx23-rtc", "fsl,stmp3xxx-rtc";
 				reg = <0x8005c000 2000>;
-				status = "disabled";
+				interrupts = <22>;
 			};
 
 			pwm@80064000 {

arch/arm/boot/dts/imx28.dtsi

@@ -503,9 +503,9 @@
 			};
 
 			rtc@80056000 {
+				compatible = "fsl,imx28-rtc", "fsl,stmp3xxx-rtc";
 				reg = <0x80056000 2000>;
-				interrupts = <28 29>;
-				status = "disabled";
+				interrupts = <29>;
 			};
 
 			i2c0: i2c@80058000 {