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

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 d71b36c856e3 ("arm64: dts: rockchip: add max-link-speed for
rk3399").

Fixes: 71afb86830a5 ("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.net
Signed-off-by: Heiko Stuebner <heiko@sntech.de>