Bluetooth: L2CAP: Fix invalid access on ECRED Connection response

[ Upstream commit de895b43 ]

The use of l2cap_chan_del is not safe under a loop using
list_for_each_entry.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>