netfilter: xt_HMARK: modulus is expensive for hash calculation

Use:

((u64)(HASH_VAL * HASH_SIZE)) >> 32

as suggested by David S. Miller.
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/xt_HMARK.c

@@ -109,7 +109,7 @@ hmark_hash(struct hmark_tuple *t, const struct xt_hmark_info *info)
 	hash = jhash_3words(t->src, t->dst, t->uports.v32, info->hashrnd);
 	hash = hash ^ (t->proto & info->proto_mask);
 
-	return (hash % info->hmodulus) + info->hoffset;
+	return (((u64)hash * info->hmodulus) >> 32) + info->hoffset;
 }
 
 static void