arm64: dts: qcom: sm8150: drop snps,dw-pcie fallback compatible

Qualcomm PCI express root complex does not use snps,dw-pcie fallback:

  ['qcom,pcie-sm8150', 'snps,dw-pcie'] is too long

Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230417080939.28648-2-krzysztof.kozlowski@linaro.org