Bluetooth: ISO: Fix CIS peripheral disconnection during setup

When the central aborts the CIS setup during the CIS Creation
procedure after it has accepted the CIS request, the peripheral
will receive the HCI LE CIS Established event with an error code.
It does not receive a disconnection event.
See the message sequence chart in Core_v5.4, Vol 6, Part D,
Section 6.23.

This commit ensures that the perirpheral disconnected callback gets
called for this particular scenario.

Signed-off-by: Rubin Gerritsen <rubin.gerritsen@nordicsemi.no>