Joining a PAN officially goes by associating with a coordinator. This
coordinator may have been discovered thanks to the beacons it sent in
the past. Add support to the MAC layer for these associations, which
require:
- Sending an association request
- Receiving an association response

The association response contains the association status, eventually a
reason if the association was unsuccessful, and finally a short address
that we should use for intra-PAN communication from now on, if we
required one (which is the default, and not yet configurable).

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
  include/net/cfg802154.h         |   1 +
  include/net/ieee802154_netdev.h |   5 ++
  net/ieee802154/core.c           |  14 ++++
  net/mac802154/cfg.c             |  70 ++++++++++++++++++
  net/mac802154/ieee802154_i.h    |  19 +++++
  net/mac802154/main.c            |   2 +
  net/mac802154/rx.c              |   9 +++
  net/mac802154/scan.c            | 127 ++++++++++++++++++++++++++++++++
  8 files changed, 247 insertions(+)

diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
index 1c22cef77425..df1f6c905c2d 100644
--- a/include/net/cfg802154.h
+++ b/include/net/cfg802154.h

@@ -503,6 +503,7 @@ struct wpan_dev {
  	struct mutex association_lock;
  	struct ieee802154_pan_device *parent;
  	struct list_head children;
+	unsigned int association_generation;