ieee802154: Add support for allowing to answer BEACON_REQ

Accept beaconing configurations from the user which involve answering
beacon requests rather than only passively sending beacons. This may
help devices to find the PAN more quickly.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230310145346.1397068-4-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
