thunderbolt: switch: Demote a bunch of non-conformant kernel-doc headers

Fixes the following W=1 kernel build warning(s):

 drivers/thunderbolt/switch.c:730: warning: Function parameter or member 'port' not described in 'tb_init_port'
 drivers/thunderbolt/switch.c:1348: warning: Function parameter or member 'sw' not described in 'tb_plug_events_active'
 drivers/thunderbolt/switch.c:1348: warning: Function parameter or member 'active' not described in 'tb_plug_events_active'

Cc: Andreas Noever <andreas.noever@gmail.com>
Cc: Michael Jamet <michael.jamet@intel.com>
Cc: Yehezkel Bernat <YehezkelShB@gmail.com>
Cc: linux-usb@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
[ mw: Demote only static functions ]
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>