nvme: Remove unused field

The "name" field in struct nvme_ctrl is unsued so removing it.
This would help save 12 bytes of space for each nvme_ctrl instance
created.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>