Bluetooth: Remove connection interval parameters from hci_conn_params_set

The connection interval parameter of hci_conn_params_set are always used
with the controller defaults. So just let hci_conn_params_add set the
controller default and not bother resetting them to controller defaults
every time the hci_conn_params_set is called.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>