st/va: disable MPEG4 by default v2

The workarounds are too hacky to enable them by default
and otherwise MPEG4 doesn't work reliably.

v2: add docs/envvars.html, CC stable and fix typos

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> (v1)
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu> (v1)
Cc: "11.1.0" <mesa-stable@lists.freedesktop.org>
2 files changed