Refactor xfs_difree() in preparation for the finobt. xfs_difree()
performs the validity checks against the ag and reads the agi
header. The work of physically updating the inode allocation btree
is pushed down into the new xfs_difree_inobt() helper.
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>