net: neterion: replace ip_fast_csum with csum_replace2

replace ip_fast_csum with csum_replace2 to save cpu cycles
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/neterion/s2io.c

@@ -80,6 +80,7 @@
 #include <linux/slab.h>
 #include <linux/prefetch.h>
 #include <net/tcp.h>
+#include <net/checksum.h>
 
 #include <asm/div64.h>
 #include <asm/irq.h>
@@ -8337,16 +8338,13 @@ static void update_L3L4_header(struct s2io_nic *sp, struct lro *lro)
 {
 	struct iphdr *ip = lro->iph;
 	struct tcphdr *tcp = lro->tcph;
-	__sum16 nchk;
 	struct swStat *swstats = &sp->mac_control.stats_info->sw_stat;
 
 	DBG_PRINT(INFO_DBG, "%s: Been here...\n", __func__);
 
 	/* Update L3 header */
+	csum_replace2(&ip->check, ip->tot_len, htons(lro->total_len));
 	ip->tot_len = htons(lro->total_len);
-	ip->check = 0;
-	nchk = ip_fast_csum((u8 *)lro->iph, ip->ihl);
-	ip->check = nchk;
 
 	/* Update L4 header */
 	tcp->ack_seq = lro->tcp_ack;