Bluetooth: hci_conn: Add support for linking multiple hcon

Since it is required for some configurations to have multiple CIS with
the same peer which is now covered by iso-tester in the following test
cases:

    ISO AC 6(i) - Success
    ISO AC 7(i) - Success
    ISO AC 8(i) - Success
    ISO AC 9(i) - Success
    ISO AC 11(i) - Success

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>