btrfs: block-group: don't set the wrong READA flag for btrfs_read_block_groups()

Regular block group items in extent tree are scattered inside the huge
tree, thus forward readahead makes no sense.
Signed-off-by: NQu Wenruo <wqu@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/block-group.c

@@ -1988,7 +1988,6 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
-	path->reada = READA_FORWARD;
 
 	cache_gen = btrfs_super_cache_generation(info->super_copy);
 	if (btrfs_test_opt(info, SPACE_CACHE) &&