virtio_net: do not rate limit counter increments

While it is desirable to rate limit certain messages, it is not
desirable to rate limit the incrementing of counters associated
with those messages.

Signed-off-by: Rick Jones <rick.jones2@hp.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>