fib: Return the correct errno code

stable inclusion
from linux-4.19.196
commit 7e3f278d55b0677aa82d07ba521390c8b090ee69

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

[ Upstream commit 59607863 ]

When kalloc or kmemdup failed, should return ENOMEM rather than ENOBUF.

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>