devfs - Add a destroy_dev_alias, remove hotplug

devfs - Add a destroy_dev_alias, remove hotplug

* Move the wildCmp* functions into devfs_core and expose them to the
  whole of devfs, but renamed as devfs_wildCmp*.

* Add a destroy_dev_alias functionality that will remove specific
  aliases to a cdev that match a given wild string.

* Remove the whole hotplug magic since it was broken already for systems
  with several devfs mount points (it would receive several attaches,
  one for each mount point). It is also redundant now that udev/devattr
  provides that functionality.