gso: Do not perform partial GSO if number of partial segments is 1 or less

In the event that the number of partial segments is equal to 1 we don't
really need to perform partial segmentation offload.  As such we should
skip multiplying the MSS and instead just clear the partial_segs value
since it will not provide any gain to advertise the frame as being GSO when
it is a single frame.
Signed-off-by: NAlexander Duyck <aduyck@mirantis.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -3101,7 +3101,10 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 	 */
 	if (features & NETIF_F_GSO_PARTIAL) {
 		partial_segs = len / mss;
-		mss *= partial_segs;
+		if (partial_segs > 1)
+			mss *= partial_segs;
+		else
+			partial_segs = 0;
 	}
 
 	headroom = skb_headroom(head_skb);