wireguard: selftests: test multiple parallel streams

wireguard: selftests: test multiple parallel streams

commit d5a49aa6c3e264a93a7d08485d66e346be0969dd upstream.

In order to test ndo_start_xmit being called in parallel, explicitly add
separate tests, which should all run on different cores. This should
help tease out bugs associated with queueing up packets from different
cores in parallel. Currently, it hasn't found those types of bugs, but
given future planned work, this is a useful regression to avoid.

Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>