arm64: dts: qcom: ipq8074: set Gen2 PCIe pcie max-link-speed

Add the generic 'max-link-speed' property to describe the Gen2 PCIe link
generation limit.
This allows the generic DWC code to configure the link speed correctly.
Signed-off-by: Robert Marko <robimarko@gmail.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230113164449.906002-4-robimarko@gmail.com

arch/arm64/boot/dts/qcom/ipq8074.dtsi

@@ -766,6 +766,7 @@ pcie1: pci@10000000 {
 			linux,pci-domain = <1>;
 			bus-range = <0x00 0xff>;
 			num-lanes = <1>;
+			max-link-speed = <2>;
 			#address-cells = <3>;
 			#size-cells = <2>;