block: fix too broad elevator check in blk_mq_free_request()

We added RQF_ELV to tell whether there's an IO scheduler attached, and
RQF_ELVPRIV tells us whether there's an IO scheduler with private data
attached. Don't check RQF_ELV in blk_mq_free_request(), what we care
about here is just if we have scheduler private data attached.

This fixes a boot crash

Fixes: 2ff0682d ("block: store elevator state in request")
Reported-by: NYi Zhang <yi.zhang@redhat.com>
Reported-by: syzbot+eb8104072aeab6cc1195@syzkaller.appspotmail.com
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-mq.c

@@ -580,7 +580,7 @@ void blk_mq_free_request(struct request *rq)
 	struct request_queue *q = rq->q;
 	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 
-	if (rq->rq_flags & (RQF_ELVPRIV | RQF_ELV)) {
+	if (rq->rq_flags & RQF_ELVPRIV) {
 		struct elevator_queue *e = q->elevator;
 
 		if (e->type->ops.finish_request)