net: Fix data-races around netdev_max_backlog.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2134161


Tested: LNST, Tier1

Upstream commit:
commit 5dcd08cd
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Tue Aug 23 10:46:46 2022 -0700

    net: Fix data-races around netdev_max_backlog.

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

    While at it, we remove the unnecessary spaces in the doc.

    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: Paolo Abeni <pabeni@redhat.com>