net: ieee802154: stop dump llsec devkeys for monitors

This patch stops dumping llsec devkeys for monitors which we don't support
yet. Otherwise we will access llsec mib which isn't initialized for
monitors.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20210405003054.256017-10-aahringo@redhat.com


Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>