myri10ge: fix rmmod crash

Rmmod myri10ge crash at free_netdev() -> netif_napi_del(), because napi
structures are already deallocated. To fix call netif_napi_del() before
kfree() at myri10ge_free_slices().

Cc: stable@kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/myri10ge/myri10ge.c

@@ -3645,6 +3645,7 @@ static void myri10ge_free_slices(struct myri10ge_priv *mgp)
 			dma_free_coherent(&pdev->dev, bytes,
 					  ss->fw_stats, ss->fw_stats_bus);
 			ss->fw_stats = NULL;
+			netif_napi_del(&ss->napi);
 		}
 	}
 	kfree(mgp->ss);