xfs: log unmount events on console

There are times, when doing triage and forensics,
that we would like to know whether a filesystem was unmounted,
or if the plug was pulled without a clean unmount.  Log
unmounts at the same level (NOTICE) as we log mounts.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_super.c

@@ -1039,6 +1039,7 @@ xfs_fs_put_super(
 {
 	struct xfs_mount	*mp = XFS_M(sb);
 
+	xfs_notice(mp, "Unmounting Filesystem");
 	xfs_filestream_unmount(mp);
 	xfs_unmountfs(mp);