Bluetooth: hci_event: drop only unbound CIS if Set CIG Parameters fails

When user tries to connect a new CIS when its CIG is not configurable,
that connection shall fail, but pre-existing connections shall not be
affected.  However, currently hci_cc_le_set_cig_params deletes all CIS
of the CIG on error so it doesn't work, even though controller shall not
change CIG/CIS configuration if the command fails.

Fix by failing on command error only the connections that are not yet
bound, so that we keep the previous CIS configuration like the
controller does.

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>