We don't have any header declaring btrfs_recover_chunk_tree() nor
btrfs_recover_superblocks(), thus W=1 gives missing-prototypes warning
on them.
Fix it by introducing a new header, rescue.h for these two functions, so
make W=1 could be much happier.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>