mac802154: declare struct ieee802154_ops as const

The ieee802154_ops structure should be never changed during runtime.
This patch declare this structure as const to avoid a runtime change.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Cc: Alan Ott <alan@signal11.us>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/drivers/net/ieee802154/cc2520.c b/drivers/net/ieee802154/cc2520.c
index a31b5b6..b479c9d 100644
--- a/drivers/net/ieee802154/cc2520.c
+++ b/drivers/net/ieee802154/cc2520.c
@@ -631,7 +631,7 @@
 	return 0;
 }
 
-static struct ieee802154_ops cc2520_ops = {
+static const struct ieee802154_ops cc2520_ops = {
 	.owner = THIS_MODULE,
 	.start = cc2520_start,
 	.stop = cc2520_stop,