net: ieee802154: stop dump llsec seclevels for monitors

This patch stops dumping llsec seclevels 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/20210405003054.256017-13-aahringo@redhat.com


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