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 <claudiu.beznea.uj@bp.renesas.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20240822152801.602318-12-claudiu.beznea.uj@bp.renesas.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>