dt-bindings: phy: Add qcom,snps-eusb2-phy schema file

The SM8550 SoC uses Synopsis eUSB2 PHY. Add a dt-binding schema
for the new driver.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230208183421.2874423-2-abel.vesa@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>