The driver's interaction with the host nvme transport has been incorrect
for a while. The driver did not wait for the unregister callbacks
(waited only 5 jiffies). Thus the driver may remove objects that may be
referenced by subsequent abort commands from the transport, and the
actual unregister callback was effectively a noop. This was especially
problematic if the driver was unloaded.

The driver now waits for the unregister callbacks, as it should, before
continuing with teardown.
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>