[XFS] kill XFS_DINODE_VERSION_ defines

These names don't add any value at all over just using the numerical
values.

(First sent on October 9th)

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Niv Sardi <xaiki@sgi.com>