mac802154: correct a typo in ieee802154_alloc_device() prototype

This has no other impact than a cosmetic one.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/mac802154.h

@@ -133,7 +133,7 @@ struct ieee802154_ops {
 
 /* Basic interface to register ieee802154 device */
 struct ieee802154_dev *
-ieee802154_alloc_device(size_t priv_data_lex, struct ieee802154_ops *ops);
+ieee802154_alloc_device(size_t priv_data_len, struct ieee802154_ops *ops);
 void ieee802154_free_device(struct ieee802154_dev *dev);
 int ieee802154_register_device(struct ieee802154_dev *dev);
 void ieee802154_unregister_device(struct ieee802154_dev *dev);