netfilter: nftables: add helper function to set the base sequence number

stable inclusion
from stable-v5.10.138
commit 06fde3cd0b536ad5f992af08af114deba362fe36
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=06fde3cd0b536ad5f992af08af114deba362fe36



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[ Upstream commit 802b8051 ]

This patch adds a helper function to calculate the base sequence number
field that is stored in the nfnetlink header. Use the helper function
whenever possible.

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>