trivial: net/mac802154: Fix Kconfig typo

Signed-off-by: Julien Catalano <julien.catalano@gmail.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/mac802154/Kconfig

@@ -16,5 +16,5 @@ config MAC802154
 	  been tested yet!
 
 	  If you plan to use HardMAC IEEE 802.15.4 devices, you can
-	  say N here. Alternatievly you can say M to compile it as
+	  say N here. Alternatively you can say M to compile it as
 	  module.