Merge branch 'so_txtime-improvements'

Willem de Bruijn says:

====================
SO_TXTIME improvements

FQ targets monotonic timestamps as generated by the TCP stack.

But SO_TXTIME was later added, which can send skbs with timestamps
against other clocks. It is now possible to detect these through skb
tstamp_type.

Make FQ robust by converting these timestamps for use in FQ (patch 2).

This also requires testing against out-of-bounds values. Prefer to do
this at the source, when parsing SCM_TXTIME (patch 1). But, tests in
the hot path are still needed, to handle BPF sources.

Extend the so_txtime selftest to handle this new case (patch 3).

v1: https://lore.kernel.org/20260603190243.2789335-1-willemdebruijn.kernel@gmail.com
====================

Link: https://patch.msgid.link/20260604194221.3319080-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>