vrend: report compute cap on GL only if the GL version is at least 3.3

We requre version 330 when we create a compute shader on OpenGL, so we
should also report the cap only when we have this version.

Closes #200

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
1 file changed