netfilter: add helper function to set up the nfnetlink header and use it

stable inclusion
from stable-v5.10.138
commit bd6165b8023288a8a6fe0d65b7b446e69596fdbb
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60QFD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bd6165b8023288a8a6fe0d65b7b446e69596fdbb



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[ Upstream commit 19c28b13 ]

This patch adds a helper function to set up the netlink and nfnetlink headers.
Update existing codebase to use it.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>