arm64: dts: qcom: sc7280: drop PCIe PHY clock index

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

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Fixes: bd7d507935ca ("arm64: dts: qcom: sc7280: Add pcie clock support")
Fixes: 92e0ee9f83b3 ("arm64: dts: qcom: sc7280: Add PCIe and PHY related  nodes")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220705114032.22787-2-johan+linaro@kernel.org