ramips: remove erroneous "wdt rst" DTS entries

Remove reference to pinmux group "wdt rst" on EW1200, ZBT-WG2626 and
ZBT-WG3526 devices. "wdt rst" is a pinmux function and not a pinmux
group.

Fixes the following error message during boot:

  rt2880-pinmux pinctrl: invalid group "wdt rst" for function "gpio"

Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk>

target/linux/ramips/dts/EW1200.dts

@@ -121,7 +121,7 @@
 &pinctrl {
 	state_default: pinctrl0 {
 		gpio {
-			ralink,group = "wdt", "rgmii2", "wdt rst", "jtag", "mdio";
+			ralink,group = "wdt", "rgmii2", "jtag", "mdio";
 			ralink,function = "gpio";
 		};
 	};

target/linux/ramips/dts/ZBT-WG2626.dts

@@ -116,7 +116,7 @@
 &pinctrl {
 	state_default: pinctrl0 {
 		gpio {
-			ralink,group = "wdt", "rgmii2", "wdt rst", "jtag", "mdio";
+			ralink,group = "wdt", "rgmii2", "jtag", "mdio";
 			ralink,function = "gpio";
 		};
 	};

target/linux/ramips/dts/ZBT-WG3526.dtsi

@@ -111,7 +111,7 @@
 &pinctrl {
 	state_default: pinctrl0 {
 		gpio {
-			ralink,group = "wdt", "rgmii2", "wdt rst", "jtag", "mdio";
+			ralink,group = "wdt", "rgmii2", "jtag", "mdio";
 			ralink,function = "gpio";
 		};
 	};