e1000 linkage fix

ia64:

 drivers/built-in.o(.text+0xd9a72): In function `e1000_xmit_frame':
 : undefined reference to `csum_ipv6_magic'

Cc: Auke Kok <auke-jan.h.kok@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/net/e1000/e1000_main.c

@@ -27,6 +27,7 @@
 *******************************************************************************/
 
 #include "e1000.h"
+#include <net/ip6_checksum.h>
 
 char e1000_driver_name[] = "e1000";
 static char e1000_driver_string[] = "Intel(R) PRO/1000 Network Driver";