Bluetooth: hci_core: Rework hci_conn_params flags

This reworks hci_conn_params flags to use bitmap_* helpers and add
support for setting the supported flags in hdev->conn_flags so it can
easily be accessed.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>