arm64: dts: qcom: sm8350: drop USB PHY clock index

The QMP USB PHY provides a single clock so drop the redundant clock
index.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220705114032.22787-8-johan+linaro@kernel.org