Merge branch 'xsk-tailroom-reservation-and-mtu-validation'

Maciej Fijalkowski says:

====================
xsk: tailroom reservation and MTU validation

here we fix a long-standing issue regarding multi-buffer scenario in ZC
mode - we have not been providing space at the end of the buffer where
multi-buffer XDP works on skb_shared_info. This has been brought to our
attention via [0].

Unaligned mode does not get any specific treatment, it is user's
responsibility to properly handle XSK addresses in queues.

With adjustments included here in this set against xskxceiver I have
been able to pass the full test suite on ice.

[0]: https://community.intel.com/t5/Ethernet-Products/X710-XDP-Packet-Corruption-Issue-DRV-MODE-Zero-Copy-Multi-Buffer/m-p/1724208
====================

Link: https://patch.msgid.link/20260402154958.562179-1-maciej.fijalkowski@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>