ip: Fix data-races around sysctl_ip_default_ttl.

Bugzilla: https://bugzilla.redhat.com/2137471


Upstream Status: kernel/git/davem/net-next.git
Conflicts: partial backport only

commit 8281b7ec
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Wed Jul 13 13:51:51 2022 -0700

    ip: Fix data-races around sysctl_ip_default_ttl.

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

    Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Stefan Assmann <sassmann@redhat.com>