Merge branch 'xsk-refactors-around-generic-xmit-side'

Maciej Fijalkowski says:

====================
xsk: refactors around generic xmit side

this small patchset is about refactoring code around xsk_build_skb() as
it became pretty heavy. Generic xmit is a bit hard to follow so here are
three clean ups to start with making this code more friendly.

v1: https://lore.kernel.org/20250922152600.2455136-1-maciej.fijalkowski@intel.com
====================

Link: https://patch.msgid.link/20250925160009.2474816-1-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>