arm64: dts: rockchip: Enable PCIe for Radxa Rock Pi 4 board

Radxa Rock Pi 4 is equipped with M.2 PCIe slot,
so enable PCIe for the board.

The changes has been tested with Intel SSD 660p series device.

    01:00.0 Class 0108: Device 8086:f1a8 (rev 03)

Signed-off-by: Matwey V. Kornilov <matwey@sai.msu.ru>
Link: https://lore.kernel.org/r/20191117101545.6406-1-matwey@sai.msu.ru


Signed-off-by: Heiko Stuebner <heiko@sntech.de>