rps: rps_sock_flow_table is mostly read

Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -2205,7 +2205,7 @@ DEFINE_PER_CPU(struct netif_rx_stats, netdev_rx_stat) = { 0, };
 #ifdef CONFIG_RPS
 
 /* One global table that all flow-based protocols share. */
-struct rps_sock_flow_table *rps_sock_flow_table;
+struct rps_sock_flow_table *rps_sock_flow_table __read_mostly;
 EXPORT_SYMBOL(rps_sock_flow_table);
 
 /*