arm64: dts: rockchip: add PCIe for M.2 E-Key to rock-5b

Enable PCIe2_0 controller and its voltage supply, which is routed
to the M.2 E-Key on the upper side of the Radxa Rock 5B.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230918141451.131247-4-sebastian.reichel@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>