Input: wacom - check for bluetooth protocol while setting OLEDs

Bluetooth Intuos 4 use 1-bit definition while the USB ones use a 4-bits
definition. This changes the size of the raw image we receive, and thus
the kernel will only accept 1-bit images for Bluetooth and 4-bits for
USB.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Przemo Firszt <przemo@firszt.eu>
Reviewed-by: Ping Cheng <pingc@wacom.com>
Tested-by: Przemo Firszt <przemo@firszt.eu>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>