USB: serial: kl5kusb105: make logging less verbose

Replace a couple of dev_info with dev_dbg and remove another.

Also use the port device for logging, and include a radix prefix when
logging the baudrate.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>