[NET] ppp: Remove unnecessary pskb_may_pull

In ppp_receive_nonmp_frame, we call pskb_may_pull(skb, skb->len) if the
tailroom is >= 124.  This is pointless because this pskb_may_pull is only
needed if the skb is non-linear.  However, if it is non-linear then the
tailroom would be zero.

So it can be safely removed.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ppp_generic.c

@@ -1609,8 +1609,6 @@ ppp_receive_nonmp_frame(struct ppp *ppp, struct sk_buff *skb)
 			kfree_skb(skb);
 			skb = ns;
 		}
-		else if (!pskb_may_pull(skb, skb->len))
-			goto err;
 		else
 			skb->ip_summed = CHECKSUM_NONE;