Bluetooth: Use only 2 bits for controller type information

The controller type is limited to BR/EDR/LE and AMP controllers. This
can be easily encoded with just 2 bits and still leave enough room
for future controller types.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>