[NET]: Fix warnings in 3c523.c and ni52.c

We have to put back the cast to "char *" because these
pointers are volatile.

Reported by Andrew Morton.
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/3c523.c

@@ -1145,7 +1145,7 @@ static int elmc_send_packet(struct sk_buff *skb, struct net_device *dev)
 
 	if (len != skb->len)
 		memset((char *) p->xmit_cbuffs[p->xmit_count], 0, ETH_ZLEN);
-	skb_copy_from_linear_data(skb, p->xmit_cbuffs[p->xmit_count], skb->len);
+	skb_copy_from_linear_data(skb, (char *) p->xmit_cbuffs[p->xmit_count], skb->len);
 
 #if (NUM_XMIT_BUFFS == 1)
 #ifdef NO_NOPCOMMANDS

drivers/net/ni52.c

@@ -1182,7 +1182,7 @@ static int ni52_send_packet(struct sk_buff *skb, struct net_device *dev)
 	else
 #endif
 	{
-		skb_copy_from_linear_data(skb, p->xmit_cbuffs[p->xmit_count], skb->len);
+		skb_copy_from_linear_data(skb, (char *) p->xmit_cbuffs[p->xmit_count], skb->len);
 		len = skb->len;
 		if (len < ETH_ZLEN) {
 			len = ETH_ZLEN;