cassini: Only use chip checksum for ipv4 packets.

According to David Monro, at least with Natsemi Saturn chips the
cassini driver has some trouble with ipv6 checksums.

Until we have more information about what's going on here, only
use the chip checksums for ipv4.

This workaround was suggested and tested by David.

Update version and release date.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/cassini.c

@@ -142,8 +142,8 @@
 
 #define DRV_MODULE_NAME		"cassini"
 #define PFX DRV_MODULE_NAME	": "
-#define DRV_MODULE_VERSION	"1.5"
-#define DRV_MODULE_RELDATE	"4 Jan 2008"
+#define DRV_MODULE_VERSION	"1.6"
+#define DRV_MODULE_RELDATE	"21 May 2008"
 
 #define CAS_DEF_MSG_ENABLE	  \
 	(NETIF_MSG_DRV		| \
@@ -2136,9 +2136,12 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 		if (addr)
 			cas_page_unmap(addr);
 	}
-	skb->csum = csum_unfold(~csum);
-	skb->ip_summed = CHECKSUM_COMPLETE;
 	skb->protocol = eth_type_trans(skb, cp->dev);
+	if (skb->protocol == htons(ETH_P_IP)) {
+		skb->csum = csum_unfold(~csum);
+		skb->ip_summed = CHECKSUM_COMPLETE;
+	} else
+		skb->ip_summed = CHECKSUM_NONE;
 	return len;
 }