Merge branch 'tsnep-xdp-socket-zero-copy-support'

Gerhard Engleder says:

====================
tsnep: XDP socket zero-copy support

Implement XDP socket zero-copy support for tsnep driver. I tried to
follow existing drivers like igc as far as possible. But one main
difference is that tsnep does not need any reconfiguration for XDP BPF
program setup. So I decided to keep this behavior no matter if a XSK
pool is used or not. As a result, tsnep starts using the XSK pool even
if no XDP BPF program is available.

Another difference is that I tried to prevent potentially failing
allocations during XSK pool setup. E.g. both memory models for page pool
and XSK pool are registered all the time. Thus, XSK pool setup cannot
end up with not working queues.

Some prework is done to reduce the last two XSK commits to actual XSK
changes.
====================

Link: https://lore.kernel.org/r/20230421194656.48063-1-gerhard@engleder-embedded.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>