Merge branch 'net-tcp-dynamically-disable-tcp-md5-static-key'

Dmitry Safonov says:

====================
net/tcp: Dynamically disable TCP-MD5 static key

The static key introduced by commit 6015c71e

 ("tcp: md5: add
tcp_md5_needed jump label") is a fast-path optimization aimed at
avoiding a cache line miss.
Once an MD5 key is introduced in the system the static key is enabled
and never disabled. Address this by disabling the static key when
the last tcp_md5sig_info in system is destroyed.

Previously it was submitted as a part of TCP-AO patches set [1].
Now in attempt to split 36 patches submission, I send this independently.

Version 5:
https://lore.kernel.org/all/20221122185534.308643-1-dima@arista.com/T/#u
Version 4:
https://lore.kernel.org/all/20221115211905.1685426-1-dima@arista.com/T/#u
Version 3:
https://lore.kernel.org/all/20221111212320.1386566-1-dima@arista.com/T/#u
Version 2:
https://lore.kernel.org/all/20221103212524.865762-1-dima@arista.com/T/#u
Version 1:
https://lore.kernel.org/all/20221102211350.625011-1-dima@arista.com/T/#u

[1]: https://lore.kernel.org/all/20221027204347.529913-1-dima@arista.com/T/#u
====================

Link: https://lore.kernel.org/r/20221123173859.473629-1-dima@arista.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>