mac802154: cfg: add suspend and resume callbacks

This patch introduces suspend and resume callbacks to mac802154. When
doing suspend we calling the stop driver callback which should stop the
receiving of frames. A transceiver should go into low-power mode then.
Calling resume will call the start driver callback, which starts receiving
again and allow to transmit frames.

This was tested only with the fakelb driver and a qemu vm by doing the
following commands:

echo "devices" > /sys/power/pm_test
echo "freeze" > /sys/power/state

while doing some high traffic between two fakelb phys.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/mac802154/rx.c b/net/mac802154/rx.c
index d93ad2d..5a258c1 100644
--- a/net/mac802154/rx.c
+++ b/net/mac802154/rx.c
@@ -253,6 +253,9 @@
 
 	WARN_ON_ONCE(softirq_count() == 0);
 
+	if (local->suspended)
+		goto drop;
+
 	/* TODO: When a transceiver omits the checksum here, we
 	 * add an own calculated one. This is currently an ugly
 	 * solution because the monitor needs a crc here.
@@ -273,8 +276,7 @@
 		crc = crc_ccitt(0, skb->data, skb->len);
 		if (crc) {
 			rcu_read_unlock();
-			kfree_skb(skb);
-			return;
+			goto drop;
 		}
 	}
 	/* remove crc */
@@ -283,6 +285,10 @@
 	__ieee802154_rx_handle_packet(local, skb);
 
 	rcu_read_unlock();
+
+	return;
+drop:
+	kfree_skb(skb);
 }
 EXPORT_SYMBOL(ieee802154_rx);