kernel: add kmod-nvme package

kernel: add kmod-nvme package

Add driver for NVM Express block devices, ie. PCIe connected SSDs.

Targets which allow booting from NVMe (x86, maybe some mvebu boards come
to mind) should have it built-in, so rootfs can be mounted from there.
For targets without NVMe support in bootloader or BIOS/firmware it's
sufficient to provide the kernel module package.

On targets having the NVMe driver built-in the resulting kmod package
is an empty dummy. In any case, depending on or installing kmod-nvme
results in driver support being available (either because it was already
built-in or because the relevant kernel modules are added and loaded).

Signed-off-by: Daniel Golle <daniel@makrotopia.org>