btrfs: make btrfs_should_delete_dir_index() return a bool instead

btrfs: make btrfs_should_delete_dir_index() return a bool instead

There's no need to return errors and we currently return 1 in case the
index should be deleted and 0 otherwise, so change the return type from
int to bool as this is a boolean function and it's more clear this way.

Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>