MAINTAINERS: add missing headers in 802.15.4

This patch adds a lot of include headers which are missing by the
current IEEE 802.15.4 subsystem.
Signed-off-by: NAlexander Aring <alex.aring@gmail.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

MAINTAINERS

@@ -4689,6 +4689,13 @@ S:	Maintained
 F:	net/ieee802154/
 F:	net/mac802154/
 F:	drivers/net/ieee802154/
+F:	include/linux/nl802154.h
+F:	include/linux/ieee802154.h
+F:	include/net/nl802154.h
+F:	include/net/mac802154.h
+F:	include/net/af_ieee802154.h
+F:	include/net/cfg802154.h
+F:	include/net/ieee802154_netdev.h
 F:	Documentation/networking/ieee802154.txt
 
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