xfs: enable sparse inode chunks for v5 superblocks

Enable mounting of filesystems with sparse inode support enabled. Add
the incompat. feature bit to the *_ALL mask.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>