null_blk: fix module name at log message

The name of the module is "null_blk", not "null". Make `pr_info()` follow
the pattern of `pr_err()` log messages.

Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed