ip: Fix data-races around sysctl_ip_fwd_update_priority.

mainline inclusion
from mainline-v5.19-rc8
commit 7bf9e18d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8P5HO
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7bf9e18d9a5e99e3c83482973557e9f047b051e7



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

While reading sysctl_ip_fwd_update_priority, it can be changed
concurrently.  Thus, we need to add READ_ONCE() to its readers.

Fixes: 432e05d3 ("net: ipv4: Control SKB reprioritization after forwarding")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Conflicts:
	drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

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