ipv4: Fix ip-header identification for gso packets.

ip-header id needs to be incremented even if IP_DF flag is set.
This behaviour was changed in commit 490ab08127cebc25e3a26
(IP_GRE: Fix IP-Identification).

Following patch fixes it so that identification is always
incremented.

Reported-by: Cong Wang <amwang@redhat.com>
Acked-by: Cong Wang <amwang@redhat.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 9e5882c..70b2d4c 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1334,8 +1334,7 @@
 				iph->frag_off |= htons(IP_MF);
 			offset += (skb->len - skb->mac_len - iph->ihl * 4);
 		} else  {
-			if (!(iph->frag_off & htons(IP_DF)))
-				iph->id = htons(id++);
+			iph->id = htons(id++);
 		}
 		iph->tot_len = htons(skb->len - skb->mac_len);
 		iph->check = 0;