ieee820154: add pan_id setting support

This patch adds support for setting pan_id via nl802154 framework.
Adding a comment because setting 0xffff as pan_id seems to be valid
setting. The pan_id 0xffff as source pan is invalid. I am not sure now
about this setting but for the current netlink interface this is an
invalid setting, so we do the same now. Maybe we need to change that
when we have coordinator support and association support.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/include/linux/ieee802154.h b/include/linux/ieee802154.h
index d043449..d4037987 100644
--- a/include/linux/ieee802154.h
+++ b/include/linux/ieee802154.h
@@ -30,6 +30,8 @@
 #define IEEE802154_MTU			127
 #define IEEE802154_MIN_PSDU_LEN		5
 
+#define IEEE802154_PAN_ID_BROADCAST	0xffff
+
 #define IEEE802154_EXTENDED_ADDR_LEN	8
 
 #define IEEE802154_FC_TYPE_BEACON	0x0	/* Frame is beacon */