hid-nintendo.c: add sysfs interface for bt manual pairing

[maximus64]

Add sysfs interface to allow the host to do bluetooth manual pairing over USB interface. The host can initiate manual pairing by writing the adapter address to the sysfs bt_pair interface. That will then trigger the manual pair sequence with the controller and then the host can get the pairing key by reading back from the sysfs. The address of the device can be retrieved by the bt_mac sysfs interface.

Signed-off-by: Khoa Hoang [email protected]