i965/gen7: Enable EXT_transform_feedback extension under 3.0 override.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Paul Berry <stereotype441@gmail.com>

src/mesa/drivers/dri/intel/intel_extensions.c

@@ -104,7 +104,7 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Const.GLSLVersion = 120;
    _mesa_override_glsl_version(ctx);
 
-   if (intel->gen == 6)
+   if (intel->gen == 6 || (intel->gen == 7 && override_version >= 30))
       ctx->Extensions.EXT_transform_feedback = true;
 
    if (intel->gen >= 5)