[SCSI] qla2xxx: negative error return in qla2x00_change_queue_depth()

The *change_queue_depth functions usually return a negative error return.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>