bcachefs: Fix iterator picking

comparison was wrong
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -2058,7 +2058,7 @@ struct btree_iter *__bch2_trans_get_iter(struct btree_trans *trans,
 			continue;
 
 		if (best &&
-		    bkey_cmp(bpos_diff(best->pos, pos),
+		    bkey_cmp(bpos_diff(best->real_pos, pos),
 			     bpos_diff(iter->real_pos, pos)) < 0)
 			continue;