Move xfs.txt to admin-guide, convert xfs.txt to ReST and broken references
Signed-off-by: NSheriff Esseson <sheriffesseson@gmail.com>
Reviewed-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>