dt-bindings: usb: Add H616 compatible string

The H616 has four PHYs as the H3, along with their respective clock
gates and resets, so the property description is identical.

However the PHYs itself need some special bits, so we need a new
compatible string for it.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210519104152.21119-9-andre.przywara@arm.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/phy/allwinner,sun8i-h3-usb-phy.yaml

@@ -15,7 +15,9 @@ properties:
     const: 1
 
   compatible:
-    const: allwinner,sun8i-h3-usb-phy
+    enum:
+      - allwinner,sun8i-h3-usb-phy
+      - allwinner,sun50i-h616-usb-phy
 
   reg:
     items: