Bluetooth: Add signal handlers for channel moves

AMP channels can be moved between BR/EDR and AMP controllers using a
sequence of signals. Every attempted channel move involves a series of
four signals:

   Move Initiator                 Move Responder
        |                                 |
        |       Move Channel Request      |
        |  ---------------------------->  |
        |                                 |
        |       Move Channel Response     |
        |  <----------------------------  |
        |                                 |
        |       Move Channel Confirm      |
        |  ---------------------------->  |
        |                                 |
        |  Move Channel Confirm Response  |
	|  <----------------------------  |

All four signals are sent even if the move fails.

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 F. Padovan <padovan@profusion.mobi>