gnrc_mac: add l2 address into netdev2.

sys/include/net/gnrc/mac/types.h

@@ -29,9 +29,9 @@
 #include <xtimer.h>
 #include <net/netdev2.h>
 #include <net/gnrc/netdev2.h>
+#include <net/gnrc/netif/hdr.h>
 #include <net/gnrc.h>
 
-
 #ifdef __cplusplus
 extern "C" {
 #endif

sys/include/net/gnrc/netdev2.h

@@ -102,6 +102,16 @@ typedef struct gnrc_netdev2 {
      * @brief general information for the MAC protocol
      */
     uint16_t mac_info;
+
+    /**
+     * @brief device's l2 address
+     */
+    uint8_t  l2_addr[GNRC_NETIF_HDR_L2ADDR_MAX_LEN];
+
+    /**
+     * @brief device's l2 address length
+     */
+    uint8_t  l2_addr_len;
 #endif
 } gnrc_netdev2_t;