arm64: dts: rockchip: Use only supported PCIe link speed on Pinebook Pro

On Pinebook Pro laptops with an NVMe SSD installed, prevent random
crashes in the NVMe driver by not attempting to use a PCIe link speed
higher than that supported by the RK3399 SoC.

See commit 712fa177 ("arm64: dts: rockchip: add max-link-speed for
rk3399").

Fixes: 5a65505a ("arm64: dts: rockchip: Add initial support for Pinebook Pro")
Signed-off-by: Simon South <simon@simonsouth.net>
Link: https://lore.kernel.org/r/20200930185627.5918-1-simon@simonsouth.netSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-pinebook-pro.dts

@@ -790,7 +790,6 @@ &pcie_phy {
 &pcie0 {
 	bus-scan-delay-ms = <1000>;
 	ep-gpios = <&gpio2 RK_PD4 GPIO_ACTIVE_HIGH>;
-	max-link-speed = <2>;
 	num-lanes = <4>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&pcie_clkreqn_cpm>;