selftests: drv-net: don't assume device has only 2 queues

The test is implicitly assuming the device only has 2 queues.
A real device will likely have more. The exact problem is that
because NAPIs get added to the list from the head, the netlink
dump reports them in reverse order. So the naive napis[0] will
actually likely give us the _last_ NAPI, not the first one.
Re-enable all the NAPIs instead of hard-coding 2 in the test.
This way the NAPIs we operated on will always reappear,
doesn't matter where they were in the registration order.

Fixes: e6d76268 ("net: Update threaded state in napi config in netif_set_threaded")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20250809001205.1147153-2-kuba@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>