Bluetooth: 6LoWPAN: Create a kernel module

Instead of adding the 6LoWPAN functionality to Bluetooth module,
we create a separate kernel module for it.

Usage:

In the slave side do this:

$ modprobe bluetooth_6lowpan
$ echo 62 > /sys/kernel/debug/bluetooth/6lowpan_psm
$ hciconfig hci0 leadv

In the master side do this:

$ modprobe bluetooth_6lowpan
$ echo 62 > /sys/kernel/debug/bluetooth/6lowpan_psm
$ echo 'connect E0:06:E6:B7:2A:73 1' > \
                  /sys/kernel/debug/bluetooth/6lowpan_control

The 6LoWPAN functionality can be controlled by psm value. If it
is left to 0, then the module is disabled and all the 6LoWPAN
connections are dropped if there were any. In the above example,
the psm value is just an example and not a real value for
6LoWPAN service. The real psm value is yet to be defined in
Bluetooth specification.

The 6lowpan controlling interface is a temporary solution
until the specifications are ready.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>