net: ethernet: mediatek: enhance with avoiding superfluous assignment inside mtk_get_ethtool_stats

data_src is unchanged inside the loop, so this patch moves
the assignment to outside the loop to avoid unnecessarily
assignment

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -2137,8 +2137,9 @@ static void mtk_get_ethtool_stats(struct net_device *dev,
 		}
 	}
 
+	data_src = (u64 *)hwstats;
+
 	do {
-		data_src = (u64 *)hwstats;
 		data_dst = data;
 		start = u64_stats_fetch_begin_irq(&hwstats->syncp);