Merge branch 'xdp-a-fistful-of-generic-changes-pt-ii'

Alexander Lobakin says:

====================
xdp: a fistful of generic changes pt. II (part)

XDP for idpf is currently 5.5 chapters:
* convert Rx to libeth;
* convert Tx and stats to libeth;
* generic XDP and XSk code changes;
* generic XDP and XSk code additions (you are here);
* actual XDP for idpf via new libeth_xdp;
* XSk for idpf (via ^).

Part III.2.1 does the following:
* allows mixing pages from several Page Pools within one XDP frame;
* optimizes &xdp_frame structure and removes no-more-used field;

Everything is prereq for libeth_xdp, but will be useful standalone
as well: faster xdp_return_frame_bulk() and xdp_frame fields access.
====================

Link: https://patch.msgid.link/20241211172649.761483-1-aleksander.lobakin@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>