ARM: dts: imx7s: correct iomuxc gpr mux controller cells

Per binding doc reg-mux.yaml, the #mux-control-cells should be 1
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Marco Felsch <m.felsch@pengutronix.de>
Fixes: 94a905a7 ("ARM: dts: imx7s: add multiplexer controls")
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx7s.dtsi

@@ -513,7 +513,7 @@ gpr: iomuxc-gpr@30340000 {
 
 				mux: mux-controller {
 					compatible = "mmio-mux";
-					#mux-control-cells = <0>;
+					#mux-control-cells = <1>;
 					mux-reg-masks = <0x14 0x00000010>;
 				};