libfrog: move topology.[ch] to libxfs

libfrog: move topology.[ch] to libxfs

The topology code depends on a few libxfs structures and is only needed
by mkfs and xfs_repair.  Move this code to libxfs to reduce the size of
libfrog and to avoid build failures caused by "xfs: move perag structure
and setup to libxfs/xfs_ag.[ch]".

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>