Bluetooth: controller: Refactor BT_CTLR_ADV_INDICATION feature

Refactor BT_CTLR_ADV_INDICATION feature by moving the
implementation closer to the implementation that is closing
the advertisement event so that in the future new members
can be added as necessary (example, advertised channels).

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>