ramips: added gpio spi refclk support for wrtnode board

This syncs the dts file with the one provided by the wrtnode team:
https://github.com/WRTnode/openwrt-patches/blob/master/R41508/wrtnode_factory_firmware_dts.patch

Signed-off-by: Christian Mehlis <christian@m3hlis.de>

SVN-Revision: 46359

target/linux/ramips/dts/WRTNODE.dts

@@ -76,7 +76,7 @@
 	pinctrl {
 		state_default: pinctrl0 {
 			default {
-				ralink,group = "ephy", "wled", "pa", "i2c", "wdt", "uartf";
+				ralink,group = "ephy", "wled", "pa", "i2c", "wdt", "uartf", "spi refclk";
 				ralink,function = "gpio";
 			};
 		};