Bluetooth: controller: Modify reason for local CIS_TERMINATE procedure

When executing a local CIS_TERMINATE procedure, the reason sent to the
host must be changed to match the perspective of the initiator.

According to BT Core 5.4 Vol 4, Part E, section 7.1.6, the disconnect
reason must be BT_HCI_ERR_LOCALHOST_TERM_CONN for a local disconnect.

Signed-off-by: Morten Priess <mtpr@oticon.com>