[IA64] implement csum_ipv6_magic for ia64.

The asm version is 4.4 times faster than the generic C version and
10X smaller in code size.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/include/asm-ia64/checksum.h b/include/asm-ia64/checksum.h
index bd40f475..2b78582 100644
--- a/include/asm-ia64/checksum.h
+++ b/include/asm-ia64/checksum.h
@@ -70,4 +70,10 @@
 	return (__force __sum16)~sum;
 }
 
+#define _HAVE_ARCH_IPV6_CSUM	1
+struct in6_addr;
+extern unsigned short int csum_ipv6_magic(struct in6_addr *saddr,
+	struct in6_addr *daddr, __u32 len, unsigned short proto,
+	unsigned int csum);
+
 #endif /* _ASM_IA64_CHECKSUM_H */