ARM: dts: imx28: Use correct compatible string for RTC

The "mxim" vendor prefix does not exit, though it looks like it might
have been a typo'ed "maxim". Still, no compatible string exists that
matches "maxim,ds1339". The closest is the "dallas,ds1339" and since
this node is named "rtc" that's probably the one that was intended.
Signed-off-by: NThierry Reding <treding@nvidia.com>
Reviewed-by: NFabio Estevam <festevam@gmail.com>
Acked-by: NLothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx28-tx28.dts

@@ -338,7 +338,7 @@
 	};
 
 	ds1339: rtc@68 {
-		compatible = "mxim,ds1339";
+		compatible = "dallas,ds1339";
 		reg = <0x68>;
 		trickle-resistor-ohms = <250>;
 		trickle-diode-disable;