net: annotate data-races around sk->sk_dst_pending_confirm

stable inclusion
from stable-v4.19.300
commit ac41b10e834f5f7479f91220668e90c505808d1c
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8UH13


CVE: NA

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[ Upstream commit eb44ad4e635132754bfbcb18103f1dcb7058aedd ]

This field can be read or written without socket lock being held.

Add annotations to avoid load-store tearing.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>