nvme: don't take the I/O queue q_lock in nvme_timeout

There is nothing it protects, but it makes lockdep unhappy in many different
ways.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>