Merge branch 'xsk: Fix unaligned descriptor validation'

Kal Conley says:

====================

This patchset includes the test with the bugfix as requested here:
https://lore.kernel.org/all/f1a32d5a-03e7-fce1-f5a5-6095f365f0a9@linux.dev/

Patch #1 (the bugfix) is identical to the previous submission except
that I improved the commit message slightly.

Magnus: I improved the test code a little different than you asked
since I thought this was a little simpler than having a separate
function for now. Hopefully, you can live with this :-).
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>