ARM: dts: imx51-zii-rdu1: Fix the rtc compatible string

According to Documentation/devicetree/bindings/rtc/rtc-ds1307.txt the
original compatible "maxim,ds1341" is not a valid entry.

Switch to the documented "dallas,ds1341" compatible.
Reported-by: Chris Healy <cphealy@gmail.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Chris Healy <cphealy@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx51-zii-rdu1.dts

@@ -508,7 +508,7 @@ hpa1: amp@60 {
 	};
 
 	ds1341: rtc@68 {
-		compatible = "maxim,ds1341";
+		compatible = "dallas,ds1341";
 		reg = <0x68>;
 	};