ipv6: Fix exthdrs offload registration.

Without this fix, ipv6_exthdrs_offload_init doesn't register IPPROTO_DSTOPTS
offload, but returns 0 (as the IPPROTO_ROUTING registration actually succeeds).

This then causes the ipv6_gso_segment to drop IPv6 packets with IPPROTO_DSTOPTS
header.

The issue detected and the fix verified by running MS HCK Offload LSO test on
top of QEMU Windows guests, as this test sends IPv6 packets with
IPPROTO_DSTOPTS.
Signed-off-by: NAnton Nayshtut <anton@swortex.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/exthdrs_offload.c

@@ -25,11 +25,11 @@ int __init ipv6_exthdrs_offload_init(void)
 	int ret;
 
 	ret = inet6_add_offload(&rthdr_offload, IPPROTO_ROUTING);
-	if (!ret)
+	if (ret)
 		goto out;
 
 	ret = inet6_add_offload(&dstopt_offload, IPPROTO_DSTOPTS);
-	if (!ret)
+	if (ret)
 		goto out_rt;
 
 out: