dt-bindings: phy: Convert brcm,sr-usb-combo-phy to DT schema

Convert the Broadcom Stingray USB PHY binding to DT schema format. It's
a straight forward conversion.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20250627220126.214577-1-robh@kernel.org


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