xfs: devirtualize ->sf_get_ino and ->sf_put_ino

Replace the ->sf_get_ino and ->sf_put_ino dir ops methods with directly
called xfs_dir2_sf_get_ino and xfs_dir2_sf_put_ino helpers that take care
of the difference between the directory format with and without the file
type field.  Also move xfs_dir2_sf_get_parent_ino and
xfs_dir2_sf_put_parent_ino to xfs_dir2_sf.c with the rest of the
low-level short form entry handling and use XFS_MAXINUMBER istead of
opencoded constants.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>