mac802154: use atomic ops for sequence incrementation

This patch will use atomic operations for sequence number incrementation
while MAC header generation. Upper layers like af_802154 or 6LoWPAN
could call this function in a parallel context while generating 802.15.4
MAC header before queuing into wpan interfaces transmit queue.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
index c6aa1d2..4de59aa 100644
--- a/include/net/cfg802154.h
+++ b/include/net/cfg802154.h
@@ -177,9 +177,9 @@
 	__le64 extended_addr;
 
 	/* MAC BSN field */
-	u8 bsn;
+	atomic_t bsn;
 	/* MAC DSN field */
-	u8 dsn;
+	atomic_t dsn;
 
 	u8 min_be;
 	u8 max_be;