Input: xpad - demote non-conformant kernel-doc header

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

 drivers/input/joystick/xpad.c:1361: warning: Function parameter or member 'xpad' not described in 'xpad_send_led_command'
 drivers/input/joystick/xpad.c:1361: warning: Function parameter or member 'command' not described in 'xpad_send_led_command'
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20201112110204.2083435-2-lee.jones@linaro.orgSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/joystick/xpad.c

@@ -1337,7 +1337,7 @@ struct xpad_led {
 	struct usb_xpad *xpad;
 };
 
-/**
+/*
  * set the LEDs on Xbox360 / Wireless Controllers
  * @param command
  *  0: off