nvme-loop: do not warn for deleted controllers during reset

During concurrent reset and delete calls the reset workqueue is
flushed, causing nvme_loop_reset_ctrl_work() to be executed when
the controller is in state DELETING or DELETING_NOIO.
But this is expected, so we shouldn't issue a WARN_ON here.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>