btrfs: check-integrity: simplify bio allocation in btrfsic_read_block

btrfsic_read_block does not need the btrfs_bio structure, so switch to
plain bio_alloc (that also does not fail as it's backed by a bioset).
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/check-integrity.c

@@ -1561,10 +1561,9 @@ static int btrfsic_read_block(struct btrfsic_state *state,
 		struct bio *bio;
 		unsigned int j;
 
-		bio = btrfs_bio_alloc(num_pages - i);
-		bio_set_dev(bio, block_ctx->dev->bdev);
+		bio = bio_alloc(block_ctx->dev->bdev, num_pages - i,
+				REQ_OP_READ, GFP_NOFS);
 		bio->bi_iter.bi_sector = dev_bytenr >> 9;
-		bio->bi_opf = REQ_OP_READ;
 
 		for (j = i; j < num_pages; j++) {
 			ret = bio_add_page(bio, block_ctx->pagev[j],