net: neigh: use long type to store jiffies delta

stable inclusion
from linux-4.19.99
commit d261a03d8cac78006f2f28c6f950429f1588fb07

--------------------------------

[ Upstream commit 9d027e3a ]

A difference of two unsigned long needs long storage.

Fixes: c7fb64db ("[NETLINK]: Neighbour table configuration and statistics via rtnetlink")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NLi Aichun <liaichun@huawei.com>
Reviewed-by: Nguodeqing <geffrey.guo@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/core/neighbour.c

@@ -1885,8 +1885,8 @@ static int neightbl_fill_info(struct sk_buff *skb, struct neigh_table *tbl,
 		goto nla_put_failure;
 	{
 		unsigned long now = jiffies;
-		unsigned int flush_delta = now - tbl->last_flush;
-		unsigned int rand_delta = now - tbl->last_rand;
+		long flush_delta = now - tbl->last_flush;
+		long rand_delta = now - tbl->last_rand;
 		struct neigh_hash_table *nht;
 		struct ndt_config ndc = {
 			.ndtc_key_len		= tbl->key_len,