flow_dissector: clean up IPIP case

Explicitly set proto to ETH_P_IP and jump directly to ip processing.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/flow_dissector.c

@@ -139,7 +139,8 @@ ipv6:
 		break;
 	}
 	case IPPROTO_IPIP:
-		goto again;
+		proto = htons(ETH_P_IP);
+		goto ip;
 	default:
 		break;
 	}