Bluetooth: Convert pend_le_conn list to a generic action list

In preparation to store also HCI_AUTO_CONN_REPORT entries in a list it
makes sense to convert the existing pend_le_conn list head of
hci_conn_params into a more generically named "action". This makes sense
because a parameter entry will never participate in more than one action
list.

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