Bluetooth: Add AMP-related data and structures for channel signals

AMP channel creation and channel moves are coordinated using the L2CAP
signaling channel.  These definitions cover the "create channel",
"move channel", and "move channel confirm" signals.

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>