[c-nsp] disabling dfc card on 6500

[Ross W]

We're tracking down an issue with a dfc3bxl card on an x6748 that looks to
be memory related, and it would be very helpful if there is a way to disable
the dfc card without disabling the line card while the box is running.

I know that IOS has the ability to do it by itself if it decides to, but I'm
looking for a way to trigger that functionality from the commandline.

I've found lots of info on powering down the x6748, but that's not what I
want.  Also, I've got ios 12.2.18sxf4 running on it.

Thanks,
  Ross.