arm64: tegra: Add VCC supply for GPIO expanders on Jetson TX2

The GPIO expanders on Jetson TX2 are powered by the VDD_1V8 and
VDD_3V3_SYS supplies, respectively. Model this in device tree so that
the correct supplies are referenced.

Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra186-p2771-0000.dts

@@ -31,6 +31,8 @@
 
 			#gpio-cells = <2>;
 			gpio-controller;
+
+			vcc-supply = <&vdd_3v3_sys>;
 		};
 
 		exp2: gpio@77 {
@@ -43,6 +45,8 @@
 
 			#gpio-cells = <2>;
 			gpio-controller;
+
+			vcc-supply = <&vdd_1v8>;
 		};
 	};