ARM: dts: at91: sama5d2: use correct rtc compatible

Use the sama5d2 specific compatible string for the RTC.

Link: https://lore.kernel.org/r/20191229204421.337612-8-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

arch/arm/boot/dts/sama5d2.dtsi

@@ -695,7 +695,7 @@ clk32k: sckc@f8048050 {
 			};
 
 			rtc: rtc@f80480b0 {
-				compatible = "atmel,at91rm9200-rtc";
+				compatible = "atmel,sama5d2-rtc";
 				reg = <0xf80480b0 0x30>;
 				interrupts = <74 IRQ_TYPE_LEVEL_HIGH 7>;
 				clocks = <&clk32k>;