net: ieee802154: stop dump llsec devs for monitors

[ Upstream commit 5582d641e6740839c9b83efd1fbf9bcd00b6f5fc ]

This patch stops dumping llsec devs 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/20210405003054.256017-7-aahringo@redhat.com


Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>