On EF100, the RX hash field in the packet prefix may not be valid (e.g.
 if the header parse failed), and this is indicated by a one-bit flag
 elsewhere in the packet prefix.  Only call skb_set_hash() if the
 RSS_HASH_VALID bit is set.
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>