ath79: add pinmux node to ar724x.dtsi

Signed-off-by: Alex Maclean <monkeh@monkeh.net>

target/linux/ath79/dts/ar724x.dtsi

@@ -64,6 +64,21 @@
 				#interrupt-cells = <2>;
 			};
 
+			pinmux: pinmux@18040028 {
+				compatible = "pinctrl-single";
+
+				reg = <0x18040028 0x8>;
+
+				pinctrl-single,bit-per-mux;
+				pinctrl-single,register-width = <32>;
+				pinctrl-single,function-mask = <0x1>;
+				#pinctrl-cells = <2>;
+
+				jtag_disable_pins: pinmux_jtag_disable_pins {
+				pinctrl-single,bits = <0x0 0x1 0x1>;
+				};
+			};
+
 			pll: pll-controller@18050000 {
 				compatible = "qca,ar7240-pll", "syscon";
 				reg = <0x18050000 0x3c>;