libva: Uprev to 2.7.1.

This CL uprevs libva to the upstream release. cros_portage_upgrade
--unstable-ok is used to perform a pristine upgrade on portage-stable
and then the x11-libs/libva folder is copied to chromiumos-overlay.

After that, the following changes are made:

- We remove 9999 stuff from the ebuild because we don't expect to use
  cros_workon with this package.

- We force the use of libva over DRM because we don't expect to use it
  over X or Wayland. This involves explicitly disabling the platforms
  other than DRM according to the flags in [1].

- We only use the intel, amdgpu, and iHD video cards. Surprisingly, we
  don't seem to use i965 in Chrome OS (we use intel instead). We handle
  these video cards in the same way the old ebuild did. Note that we add
  a REQUIRED_USE to ensure that one of the video cards is being used.

See the diff since PS1 for these changes.

Also, note that we temporarily depend on iHD 19.4.0 so that this CL can
be built independently of the iHD uprev which will happen in a follow
up.

The 0001-Return-error-when-no-va-devices-available.patch file is removed
because it's included upstream on libva 2.7.1 [2].

[1] https://github.com/intel/libva/blob/2.7.1/configure.ac#L127-L155
[2] https://github.com/intel/libva/commit/48f446b32a4fe76d542c56c87f9427e8d14e073d

BUG=b:159825228
TEST=emerge-eve x11-libs/libva

Cq-Depend: chromium:2275495
Change-Id: Icdd5c2bb12a00e46042c4c1d9cfd034a15b7ea60
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2270741
Tested-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Commit-Queue: Andres Calderon Jaramillo <andrescj@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
7 files changed