ah6: fix error return code in ah6_input()

Fix to return a negative error code from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Zhang Changzhong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/ipv6/ah6.c

···
 	memcpy(auth_data, ah->auth_data, ahp->icv_trunc_len);
 	memset(ah->auth_data, 0, ahp->icv_trunc_len);
 
-	if (ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN))
+	err = ipv6_clear_mutable_options(ip6h, hdr_len, XFRM_POLICY_IN);
+	if (err)
 		goto out_free;
 
 	ip6h->priority    = 0;