bluetooth: Set 6 byte device addresses

Set BTLE MAC addresses that are 6 bytes long and not 8 bytes
that are used in other places with 6lowpan.

Signed-off-by: Patrik Flykt <patrik.flykt@linux.intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>