dt-bindings: phy: qcom,qusb2: document sdm670 compatible

The Snapdragon 670 uses the QUSB driver for USB 2.0. Document the
compatible used in the device tree.

Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220922024656.178529-2-mailingradian@gmail.com


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