dt-bindings: reset: Document RZ/V2H(P) USB2PHY reset

dt-bindings: reset: Document RZ/V2H(P) USB2PHY reset

Add a device tree binding document for the Renesas RZ/V2H(P) USB2PHY reset
controller. This block manages the reset and power-down of the USB 2.0 PHY,
which is used in both host and function modes.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Link: https://lore.kernel.org/r/20250415195131.281060-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>