ieee802154: add IEEE802154_EXTENDED_ADDR_LEN

This patch adds a new define for getting the length of an extended
address.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/linux/ieee802154.h

@@ -29,6 +29,8 @@
 #define IEEE802154_MTU			127
 #define IEEE802154_MIN_PSDU_LEN		5
 
+#define IEEE802154_EXTENDED_ADDR_LEN	8
+
 #define IEEE802154_FC_TYPE_BEACON	0x0	/* Frame is beacon */
 #define	IEEE802154_FC_TYPE_DATA		0x1	/* Frame is data */
 #define IEEE802154_FC_TYPE_ACK		0x2	/* Frame is acknowledgment */