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>