xfs: cleanup the definition of struct xfs_dir2_sf_entry
Remove the inumber member which is at a variable offset after the actual
name, and make name a real variable sized C99 array instead of the incorrect
one-sized array which confuses (not only) gcc. Based on this clean up
the helpers to calculate the entry size.
Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Alex Elder <aelder@sgi.com> Reviewed-by: Dave Chinner <dchinner@redhat.com>