thunderbolt: Notify userspace about software CM tunneling events

thunderbolt: Notify userspace about software CM tunneling events

This adds notification whenever software connection manager activates,
changes or deactivates a tunnel, and also if there is limitation in
bandwidth.

The notification looks like below:

  TUNNEL_EVENT=activated|changed|deactivated|low bandwidth|
  	       insufficient bandwidth
  TUNNEL_DETAILS=0:12 <-> 1:20 (USB3)

Userspace can then listen these and inform user if needed. For example
if there is not enough bandwidth, it can show warning dialog to the user.

Signed-off-by: Alan Borzeszkowski <alan.borzeszkowski@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>