nvme: move block_device_operations and ns/ctrl freeing to common code

nvme: move block_device_operations and ns/ctrl freeing to common code

This moves the block_device_operations over to common code mostly
as-is.  The only change is that the ns and ctrl refcounting got some
small refcounting to have wrappers around the kref_put operations.

A new free_ctrl operation is added to allow the PCI driver to free
it's ressources on the final drop.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[Moved the integrity and pr changes due to merge conflict]
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit 1673f1f08c8876f3942b4fa5e8f6a40215f15a94)

Orabug: 25130845
Conflicts:
    drivers/nvme/host/pci.c

Signed-off-by: Ashok Vairavan <ashok.vairavan@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>