arm64: tegra: Add missing #phy-cells property on Jetson AGX Xavier

PHYs need to have a #phy-cells property that defines how many cells are
required in their specifier. The standard Ethernet PHY doesn't require a
specifier, so set its #phy-cells to 0.
Signed-off-by: Thierry Reding <treding@nvidia.com>

arch/arm64/boot/dts/nvidia/tegra194-p2888.dtsi

@@ -44,6 +44,7 @@ phy: phy@0 {
 					reg = <0x0>;
 					interrupt-parent = <&gpio>;
 					interrupts = <TEGRA194_MAIN_GPIO(G, 4) IRQ_TYPE_LEVEL_LOW>;
+					#phy-cells = <0>;
 				};
 			};
 		};