ieee802154: Add support for user active scan requests

In case a passive scan could not discover any PAN, a device may decide
to perform an active scan to force coordinators to send a BEACON
"immediately". Allow users to request to perform an active scan.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230310145346.1397068-2-miquel.raynal@bootlin.com


Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>