configs: imx8mp_beacon: Enable PCIe NVMe drives

configs: imx8mp_beacon: Enable PCIe NVMe drives

The baseboard supports and NVMe drives via the PCIe slot. This
requires a few extra config options to be enabled.

The NVMe can be enumerated with the following commands:

u-boot=> pci enum
PCIE-0: Link up (Gen1-x1, Bus0)
u-boot=> nvme scan
u-boot=> nvme info
Device 0: Vendor: 0x15b7 Rev: 20120022 Prod: 184960441105
            Type: Hard Disk
            Capacity: 122104.3 MB = 119.2 GB (250069680 x 512)
u-boot=>

Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>