rockchip: jaguar-rk3588: add PCIe M.2 M-KEY NVMe support

rockchip: jaguar-rk3588: add PCIe M.2 M-KEY NVMe support

Jaguar has an M.2 M-KEY slot for NVMes, connected to the PCIe3 4-lane
PHY on RK3588.

CONFIG_PHY_ROCKCHIP_NANENG_COMBOPHY=y is technically not necessary since
it's required only for the M.2 E-KEY slot on the main PCB, but that is
used typically for WiFi+BT modules, or on the mezzanine connector but
the features exposed behind that connector aren't supported in U-Boot
(no DT for it right now). However, if the PHY driver is missing, we get
the following error message:
pcie_dw_rockchip pcie@fe170000: failed to get pcie phy (ret=-19)

and you would need to know which PCIe controller that is before deciding
to ignore it. While after enabling the PHY driver, we are greeted with:
pcie_dw_rockchip pcie@fe170000: PCIe-2 Link Fail
which is a bit more acceptable (to me).

The other option would be to disable the PCIe2 PHYs/controllers in the
DT, which I'm not too fond of.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>