ARM: dts: imx28-tx28: add trickle-charge config for DS1339

As the DS1339 driver now supports enabling the trickle charge feature
via DTB, add the appropriate properties to utilize this feature.
Signed-off-by: NLothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

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

@@ -361,6 +361,8 @@
 	ds1339: rtc@68 {
 		compatible = "mxim,ds1339";
 		reg = <0x68>;
+		trickle-resistor-ohms = <250>;
+		trickle-diode-disable;
 	};
 };