ppp: eliminate shadowed variable name

Sparse complains about shadowed declaration of skb. So use other
name.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ppp_generic.c

@@ -1927,9 +1927,9 @@ ppp_receive_mp_frame(struct ppp *ppp, struct sk_buff *skb, struct channel *pch)
 	/* If the queue is getting long, don't wait any longer for packets
 	   before the start of the queue. */
 	if (skb_queue_len(&ppp->mrq) >= PPP_MP_MAX_QLEN) {
-		struct sk_buff *skb = skb_peek(&ppp->mrq);
-		if (seq_before(ppp->minseq, skb->sequence))
-			ppp->minseq = skb->sequence;
+		struct sk_buff *mskb = skb_peek(&ppp->mrq);
+		if (seq_before(ppp->minseq, mskb->sequence))
+			ppp->minseq = mskb->sequence;
 	}
 
 	/* Pull completed packets off the queue and receive them. */