virgl: Add a caps feature check version

virgl: Add a caps feature check version

When we add new feature checks on the host side that is used to
enable a cap conditionally that was enabled unconditionally before
we might end up with a feature regression when a new mesa version
is used with an old virglrenderer version that doesn't check for
that cap.

To work around this problem add a version id to the caps that corresponds
to the features that are actually checked on the host and check that
version too when enabling the cap.

Fixes: 2ee197d6e84aa37638d423363aca183952816067
    virgl: Enable mixed color FBO attachemnets only when the host supports it

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Pohsien Wang <pwang@chromium.org>