intel: workaround VF/VS fixed function issue on Gen9 GT1 parts

The issue is noticeable in the dEQP-GLES31.functional.geometry_shading.layered.render_with_default_layer_3d test where a triangle goes missing when we use the maximum number of URB entries as specified by the documentation.

Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107505

Google's ChromeOS has been running with patch for the last ~6 months : https://chromium.googlesource.com/chromiumos/third_party/mesa/+/602ed7b9bc5ab00d628f4686c00723d2a6bd7b07