ARM: tegra: enable PCA9546 on Cardhu

Cardhu has a PCA9546 for I2C bus extension, which connects to 3
cameras. It's required for Tegra V4L2 soc camera driver and camera
sensor drivers.
Signed-off-by: Bryan Wu <pengw@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/boot/dts/tegra30-cardhu.dtsi

@@ -187,6 +187,13 @@ isl29028@44 {
 			interrupt-parent = <&gpio>;
 			interrupts = <TEGRA_GPIO(L, 0) IRQ_TYPE_LEVEL_HIGH>;
 		};
+
+		i2cmux@70 {
+			compatible = "nxp,pca9546";
+			#address-cells = <1>;
+			#size-cells = <0>;
+			reg = <0x70>;
+		};
 	};
 
 	i2c@7000c700 {