Bluetooth: Channel move request handling

On receipt of a channel move request, the request must be validated
based on the L2CAP mode, connection state, and controller
capabilities.  ERTM channels must have their state machines cleared
and transmission paused while the channel move takes place.

If the channel is being moved to an AMP controller then
an AMP physical link must be prepared.  Moving the channel back to
BR/EDR proceeds immediately.

Signed-off-by: Mat Martineau <mathewm@codeaurora.org>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Acked-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>