netfilter: nat: remove csum_recalc hook

mainline inclusion
from mainline-v5.1-rc1
commit dac3fe72
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7O0PV
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dac3fe72596f91011afc649a9d181b18466dd895



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

We can now use direct calls.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Conflicts:
	include/net/netfilter/nf_nat_l3proto.h
	net/ipv4/netfilter/nf_nat_l3proto_ipv4.c
	net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
	net/netfilter/Makefile
	net/netfilter/nf_nat_helper.c
	net/netfilter/nf_nat_proto.c

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>