thunderbolt: Add more logging to XDomain connections

Currently the driver is pretty quiet when another host is connected
which makes debugging possible issues harder. For this reason add more
logging on debug level that can be turned on as needed.

While there log the host-to-host connection on info level analogous to
routers and retimers.

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