nvmet-auth: fix a couple of spelling mistakes

There are a couple of spelling mistakes in pr_warn and pr_debug messages.
Fix them.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>