Fix this sparse warning:
  fs/xfs/xfs_da_btree.c:1550:26: warning: symbol 'xfs_default_nameops' was not declared. Should it be static?
Signed-off-by: NHannes Eder <hannes@hanneseder.net>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NFelix Blyakher <felixb@sgi.com>