ARM: dts: rockchip: rk3588s-u-boot: add pcie2x1l2 with PHY

Add the node for PCIe 2x1l 2 device together with the corresponding
combphy.

Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
[eugen.hristev@collabora.com: moved to -u-boot.dtsi, minor
adaptations]
Signed-off-by: Eugen Hristev <eugen.hristev@collabora.com>
[jonas@kwiboo.se: adapt to kernel node]
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>