[XFS] silence gcc4 warnings. the directory ones are wrong because of

information gcc could not find out (that a directory always has a ..
entry), the others are outright gcc bugs.

SGI-PV: 943511
SGI-Modid: xfs-linux:xfs-kern:200055a

Signed-off-by: Christoph Hellwig <hch@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>