usb: misc: legousbtower: Demote function header which is clearly not kerneldoc

usb: misc: legousbtower: Demote function header which is clearly not kerneldoc

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

 drivers/usb/misc/legousbtower.c:280: warning: Function parameter or member 'dev' not described in 'lego_usb_tower_debug_data'
 drivers/usb/misc/legousbtower.c:280: warning: Function parameter or member 'function' not described in 'lego_usb_tower_debug_data'
 drivers/usb/misc/legousbtower.c:280: warning: Function parameter or member 'size' not described in 'lego_usb_tower_debug_data'
 drivers/usb/misc/legousbtower.c:280: warning: Function parameter or member 'data' not described in 'lego_usb_tower_debug_data'

Cc: Juergen Stuber <starblue@users.sourceforge.net>
Cc: David Glance <davidgsf@sourceforge.net>
Cc: david <david@csse.uwa.edu.au>
Cc: legousb-devel@lists.sourceforge.net
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200706133341.476881-8-lee.jones@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>