net-rps: Fix brokeness causing OOO packets

In commit c445477d

 which adds aRFS to the kernel, the CPU
selected for RFS is not set correctly when CPU is changing.
This is causing OOO packets and probably other issues.

Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>