Bluetooth: hci_core: Make hci_conn_hash_add append to the list

This makes hci_conn_hash_add append to the tail of the conn_hash so it
matches the order they are created, this is required if the controller
attempts to match the order of ACL with CIS which uses append logic
when programming the CIS ids on the CIG.

The result of this change affects Create CIS:

Before:

< HCI Command: LE Create Connected Isochronous Stream (0x08|0x0064) plen 9
        Number of CIS: 2
        CIS Handle: 2560
        ACL Handle: 3586
        CIS Handle: 2561
        ACL Handle: 3585

After:

< HCI Command: LE Create Connected Isochronous Stream (0x08|0x0064) plen 9
        Number of CIS: 2
        CIS Handle: 2560
        ACL Handle: 3585
        CIS Handle: 2561
        ACL Handle: 3586

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