[nsp] isdn channels

[atticus at satanic.org]

> I'll keep looking.  I figured their'd be an easy way to configure a
> channel to do voice or data only, or restict the isdn modems ability to
> use channels in a certian way.

Its the wrong solution, but you should be able to configure an
invalid SPID on one of the B's, which would keep it from ever coming up
properly and likewise being a candidate for the dialer.