ieee802154: remove nl802154 unused functions

The include/net/nl802154.h file contains a lot of prototypes which are
not used inside of ieee802154 subsystem. This patch removes this file
and make the only one used prototype "ieee802154_nl_start_confirm" as
static declaration in ieee802154/nl-mac.c

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

net/mac802154/mac_cmd.c

@@ -25,7 +25,6 @@
 #include <net/ieee802154_netdev.h>
 #include <net/cfg802154.h>
 #include <net/mac802154.h>
-#include <net/nl802154.h>
 
 #include "ieee802154_i.h"
 #include "driver-ops.h"
@@ -65,11 +64,6 @@ static int mac802154_mlme_start_req(struct net_device *dev,
 		rc = ops->llsec->set_params(dev, &params, changed);
 	}
 
-	/* FIXME: add validation for unused parameters to be sane
-	 * for SoftMAC
-	 */
-	ieee802154_nl_start_confirm(dev, IEEE802154_SUCCESS);
-
 	return rc;
 }