Merge branch 'selftests-xsk-simplify-umem-setup'

Tushar Vyavahare says:

====================
selftests/xsk: simplify UMEM setup

This series simplifies UMEM handling in selftests/xsk.

It centralizes UMEM property setup through helpers, moves UMEM ownership
from ifobject to socket-owned state, and normalizes umem_size/mmap_size
usage across the touched paths.
====================

Link: https://patch.msgid.link/20260608130938.958793-1-tushar.vyavahare@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>