arm64: dts: qcom: sm8450: drop incorrect spi-max-frequency

spi-max-frequency is a property of SPI device, not the controller:

  qcom/sm8450-hdk.dtb: geniqup@8c0000: spi@880000: Unevaluated properties are not allowed ('spi-max-frequency' was unexpected

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221110152741.542024-1-krzysztof.kozlowski@linaro.org