thunderbolt: Fix some kernel-doc comments

Remove some warnings found by running scripts/kernel-doc,
which is caused by using 'make W=1'.

  drivers/thunderbolt/ctl.c:701: warning: expecting prototype for tb_cfg_start().
    Prototype was for tb_ctl_start() instead
  drivers/thunderbolt/ctl.c:722: warning: expecting prototype for tb_ctrl_stop().
    Prototype was for tb_ctl_stop() instead
  drivers/thunderbolt/ctl.c:930: warning: expecting prototype for tb_cfg_write().
    Prototype was for tb_cfg_write_raw() instead

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>