Allow bthidev_output() to not grab the bt lock, to prevent lock

Allow bthidev_output() to not grab the bt lock, to prevent lock
recursion when trying to send commands from input callbacks. Makes the
caps/num/scroll lock keys on btkbd correctly lit the leds instead of
panic'ing.
Noticed and fix tested by mlarkin@, "do whatever you want in bt" deraadt@