dt-bindings: phy: sun4i-usb-phy: Add property descriptions for H3

dt-bindings: phy: sun4i-usb-phy: Add property descriptions for H3

The Allwinner H3 SoC has 4 USB PHYs, so it needs four sets of pmu
regions, clocks, resets, and optional vbus properties. These were
not described when the H3 compatible string was added.

Fixes: 626a630e003c ("phy-sun4i-usb: Add support for the host usb-phys
		      found on the H3 SoC")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>