net: mac802154: Explain the use of ieee802154_wake/stop_queue()

net: mac802154: Explain the use of ieee802154_wake/stop_queue()

It is not straightforward to the newcomer that a single skb can
currently be sent at a time and that the internal process is to stop the
queue when processing a frame before re-enabling it.

Make this clear by documenting the ieee802154_wake/stop_queue()
helpers.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20220125122540.855604-4-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>