InterleaveRDn and InterleaveRUp only apply to G.dmt. The equivalents for ADSL2
and 2+ are BisRDn and BisRUp. In addition, the INPdown and INPup statuses are
useful when trying to track down instability on a line.

Signed-off-by: Simon Farnsworth <simon@farnz.org.uk>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>