Bluetooth: Lookup channel structure based on DCID

Processing a move channel request involves getting the channel
structure using the destination channel ID.  Previous code could only
look up using the source channel ID.

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>