arm64: dts: allwinner: a64: Orange Pi Win: Enable USB hub regulator

The Orange Pi Win has four standard USB-A sockets, connected to an
on-board USB hub. The hub's and socket's power regulators are enabled by
GPIO PD7.

Add the regulator to the DT to enable the power supply.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>