thunderbolt: Make the driver less verbose

Currently the driver logs quite a lot to the system message buffer even
when doing normal operations. This information is not useful for
ordinary users and might even annoy some.

For this reason convert most of the logs at info level to happen at
debug level instead. The nice output formatting is untouched.

Logging can be easily re-enabled by passing "thunderbolt.dyndbg" in the
kernel command line (or using the corresponding control file runtime).

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Yehezkel Bernat <yehezkelshb@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>