Bluetooth: ISO: consider right CIS when removing CIG at cleanup

When looking for CIS blocking CIG removal, consider only the CIS with
the right CIG ID. Don't try to remove CIG with unset CIG ID.

Fixes: 26afbd82

 ("Bluetooth: Add initial implementation of CIS connections")
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>