net: dummy: request ops lock

Even though dummy device doesn't really need an instance lock,
a lot of selftests use dummy so it's useful to have extra
expose to the instance lock on NIPA. Request the instance/ops
locking.

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250401163452.622454-7-sdf@fomichev.me


Signed-off-by: Jakub Kicinski <kuba@kernel.org>