arm: mvebu: dts: turris_mox: fix non-working USB port

Commit 0934dddc ("arm: a37xx: Update DTS files to version from
upstream Linux kernel") ported Linux's device-tree files for Armada 3720
SOCs. This broke USB port on Turris MOX, because in Linux' DTS the bus
voltage supply is described as a `phy-supply` property of connector
node, a mechanism that is not supported in U-Boot yet.

For now, fix this by adding `vbus-supply` to usb3 node.

Fixes: 0934dddc ("arm: a37xx: Update DTS files to version from upstream Linux kernel")
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>

arch/arm/dts/armada-3720-turris-mox-u-boot.dtsi

@@ -21,3 +21,7 @@
 };
 
 /delete-node/ &mdio;
+
+&usb3 {
+	vbus-supply = <&exp_usb3_vbus>;
+};