While it worked with the kenrel, it wasn't working with the loader.
It failed to handle dependencies correctly. The reason for that is
that we never created a nvme module with the DRIVER_MODULE, but
instead a nvme_pci and nvme_ahci module. Create a real nvme module
that nvd can be dependent on so it can import the nvme symbols it
needs from there.
Arguably, nvd should just be a simple child of nvme, but transitioning
to that (and winning that argument given why it was done this way) is
beyond the scope of this change.
Reviewed by: jhb@
Differential Revision: https://reviews.freebsd.org/D21382