arm: zynq: Use i2c-mux instead of i2cswitch for pca9548

i2c muxes should described like this.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/boot/dts/zynq-zc702.dts

@@ -112,7 +112,7 @@ &i2c0 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_i2c0_default>;
 
-	i2cswitch@74 {
+	i2c-mux@74 {
 		compatible = "nxp,pca9548";
 		#address-cells = <1>;
 		#size-cells = <0>;

arch/arm/boot/dts/zynq-zc706.dts

@@ -68,7 +68,7 @@ &i2c0 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_i2c0_default>;
 
-	i2cswitch@74 {
+	i2c-mux@74 {
 		compatible = "nxp,pca9548";
 		#address-cells = <1>;
 		#size-cells = <0>;