xfs: add the inode directory type support to XFS_IOC_FSGEOM

Add the inode type directory type support to XFS_IOC_FSGEOM
so that xfs_repair/xfs_info knows if the superblock v4 filesystem
enabled the feature.

Signed-off-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>