include: add new virtio uapi header files

Commit a08bb43a ("kvmtool: Copy Linux' up-to-date virtio headers")
copied in some of the virtio UAPI headers from the kernel tree, but
didn't include all of them, as we were relying on some of them being
provided by the distribution.

Now commit bc77bf49 ("stat: Add descriptions for new virtio_balloon
stat types") used some newer virtio balloon symbols, that some older
distros (e.g. Ubuntu 18.04) do not carry, which breaks compilation
there:
=======================
  CC       builtin-stat.o
builtin-stat.c: In function 'do_memstat':
builtin-stat.c:86:8: error: 'VIRTIO_BALLOON_S_HTLB_PGALLOC' undeclared (first use in this function); did you mean 'VIRTIO_BALLOON_S_AVAIL'?
   case VIRTIO_BALLOON_S_HTLB_PGALLOC:
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        VIRTIO_BALLOON_S_AVAIL
builtin-stat.c:86:8: note: each undeclared identifier is reported only once for each function it appears in
=======================

To fix this include the remaining virtio headers (those that we actually
need for kvmtool at the moment), from Linux v5.18.0.

Fixes: bc77bf49 ("stat: Add descriptions for new virtio_balloon stat types")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Link: https://lore.kernel.org/r/20220524150611.523910-5-andre.przywara@arm.com


Signed-off-by: Will Deacon <will@kernel.org>