dt-bindings: phy: renesas,usb2-phy: Document RZ/G3S phy bindings

Document the RZ/G3S PHY bindings. The RZ/G3S USB PHY is almost identical
with the RZ/G2L USB PHY. The difference is that there is a hardware
limitation on the max burst size used when the BUS master interface
issues a transfer request for RZ/G3S that is configured though PHY
registers.

Signed-off-by: Claudiu Beznea <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

Documentation/devicetree/bindings/phy/renesas,usb2-phy.yaml

···
   compatible:
     oneOf:
       - items:
-          - const: renesas,usb2-phy-r8a77470 # RZ/G1C
+          - enum:
+              - renesas,usb2-phy-r8a77470  # RZ/G1C
+              - renesas,usb2-phy-r9a08g045 # RZ/G3S
 
       - items:
           - enum: