blk-mq: Fix typo in comment

Fix typo in words: 'vector' and 'query'.

Signed-off-by: Gabriela Bittencourt <gabrielabittencourt00@gmail.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>