Make it easier to have completely new bus attachment points for pccard

Make it easier to have completely new bus attachment points for pccard
devices.  There may still be problems with said drivers, if so please
let me know.

o Move attach-like functionality to the nbk attach compatibility code.
o Smarter probe code: for the compatibility code probe succeeds if
  strcmp succeeds, for noncompatibility you can do anything you like.
o Get rid of some compiler warnings introduced in last commit.