arm64: dts: qcom: ipq6018: drop incorrect SPI bus spi-max-frequency

The spi-max-frequency property belongs to SPI devices, not SPI
controller:

  ipq6018-cp01-c1.dtb: spi@78b5000: 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/20230416123730.300863-1-krzysztof.kozlowski@linaro.org

arch/arm64/boot/dts/qcom/ipq6018.dtsi

@@ -458,7 +458,6 @@ blsp1_spi1: spi@78b5000 {
 			#size-cells = <0>;
 			reg = <0x0 0x078b5000 0x0 0x600>;
 			interrupts = <GIC_SPI 95 IRQ_TYPE_LEVEL_HIGH>;
-			spi-max-frequency = <50000000>;
 			clocks = <&gcc GCC_BLSP1_QUP1_SPI_APPS_CLK>,
 				 <&gcc GCC_BLSP1_AHB_CLK>;
 			clock-names = "core", "iface";
@@ -473,7 +472,6 @@ blsp1_spi2: spi@78b6000 {
 			#size-cells = <0>;
 			reg = <0x0 0x078b6000 0x0 0x600>;
 			interrupts = <GIC_SPI 96 IRQ_TYPE_LEVEL_HIGH>;
-			spi-max-frequency = <50000000>;
 			clocks = <&gcc GCC_BLSP1_QUP2_SPI_APPS_CLK>,
 				 <&gcc GCC_BLSP1_AHB_CLK>;
 			clock-names = "core", "iface";