nvme: Change namespace device name

Changes the device name for NVMe and NVMe-oF namespaces from using "ns"
to "n" to be more compatible with other operating systems. For example,
a device which was previously /dev/nvme0ns1 is now /dev/nvme0n1.

Preserves the existing functionality by creating alias from nvmeXnY to
nvmeXnsY.

Reviewed by: imp
MFC after: 1 month
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D45414

nvme/f: Use strlcpy instead of strncpy + manual string termination

Reviewed by: dab, imp
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D45153

nvmf: The in-kernel NVMe over Fabrics host

This is the client (initiator in SCSI terms) for NVMe over Fabrics.
Userland is responsible for creating a set of queue pairs and then
handing them off via an ioctl to this driver, e.g. via the 'connect'
command from nvmecontrol(8). An nvmeX new-bus device is created
at the top-level to represent the remote controller similar to PCI
nvmeX devices for PCI-express controllers.

As with nvme(4), namespace devices named /dev/nvmeXnsY are created and
pass through commands can be submitted to either the namespace devices
or the controller device. For example, 'nvmecontrol identify nvmeX'
works for a remote Fabrics controller the same as for a PCI-express
controller.

nvmf exports remote namespaces via nda(4) devices using the new NVMF
CAM transport. nvmf does not support nvd(4), only nda(4).

Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D44714