nl802154: add support for security layer

This patch adds support for accessing mac802154 llsec implementation
over nl802154. I added for a new Kconfig entry to provide this
functionality CONFIG_IEEE802154_NL802154_EXPERIMENTAL. This interface is
still in development. It provides to change security parameters and
add/del/dump entries of security tables. Later we can add also a get to
get an entry by unique identifier.

Cc: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/ieee802154/Kconfig b/net/ieee802154/Kconfig
index 1370d5b..188135b 100644
--- a/net/ieee802154/Kconfig
+++ b/net/ieee802154/Kconfig
@@ -12,6 +12,11 @@
 
 if IEEE802154
 
+config IEEE802154_NL802154_EXPERIMENTAL
+	bool "IEEE 802.15.4 experimental netlink support"
+	---help---
+	  Adds experimental netlink support for nl802154.
+
 config IEEE802154_SOCKET
 	tristate "IEEE 802.15.4 socket interface"
 	default y