mptcp: add sk_stop_timer_sync helper

stable inclusion
from stable-v4.19.312
commit 9c382bc16fa8f7499b0663398437e125cf4f763b
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9QG5Z
CVE: CVE-2024-35910

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9c382bc16fa8f7499b0663398437e125cf4f763b



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

[ Upstream commit 08b81d87 ]

This patch added a new helper sk_stop_timer_sync, it deactivates a timer
like sk_stop_timer, but waits for the handler to finish.

Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 151c9c724d05 ("tcp: properly terminate timers for kernel sockets")
Signed-off-by: Sasha Levin <sashal@kernel.org>

Conflicts:
	net/core/sock.c
[This is because we backport 584f3742.]
Signed-off-by: Liu Jian <liujian56@huawei.com>