sfc: fix sparse non static symbol warning

Fixes the following sparse warning:

drivers/net/ethernet/sfc/falcon.c:2601:6: warning:
 symbol 'falcon_pull_nic_stats' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/falcon.c

@@ -2614,7 +2614,7 @@ void falcon_start_nic_stats(struct efx_nic *efx)
 /* We don't acutally pull stats on falcon. Wait 10ms so that
  * they arrive when we call this just after start_stats
  */
-void falcon_pull_nic_stats(struct efx_nic *efx)
+static void falcon_pull_nic_stats(struct efx_nic *efx)
 {
 	msleep(10);
 }