dt-bindings: phy: renesas,usb2-phy: Add clock constraint for RZ/G2L family

The RZ/G2L family requires two clocks for USB2 PHY, which are already
defined in the DTSI files. Add a constraint in the DT binding document
to ensure validation with `dtbs_check`.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250414145729.343133-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

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

@@ -107,6 +107,9 @@ allOf:
           contains:
             const: renesas,rzg2l-usb2-phy
     then:
+      properties:
+        clocks:
+          minItems: 2
       required:
         - resets