Add the compatible strings for the USB2 PHYs found on QCOM
SM8250 & SM8350 SoCs.

Note that the SM8250 compatible is already in use in the dts and
driver implementation but was missing from the documentation.
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210115174723.7424-4-jackp@codeaurora.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>