ARM: dts: imx6: RDU2: add alias for RTC

This makes sure that the battery backed RTC is always the
primary one, regardless of the driver probe ordering.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6qdl-zii-rdu2.dtsi

@@ -49,6 +49,7 @@ chosen {
 
 	aliases {
 		mdio-gpio0 = &mdio1;
+		rtc0 = &ds1341;
 	};
 
 	mdio1: mdio {
@@ -501,7 +502,7 @@ eeprom@54 {
 		reg = <0x54>;
 	};
 
-	rtc@68 {
+	ds1341: rtc@68 {
 		compatible = "dallas,ds1341";
 		reg = <0x68>;
 	};