draw: cleanup the extra attribs

Before inserting new front face and prim id outputs cleanup
the old extra outputs, otherwise our cache will use previous
output slots which will break as soon as outputs of the current
shader don't match the last.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

src/gallium/auxiliary/draw/draw_context.c

@@ -555,6 +555,7 @@ draw_get_shader_info(const struct draw_context *draw)
 void
 draw_prepare_shader_outputs(struct draw_context *draw)
 {
+   draw_remove_extra_vertex_attribs(draw);
    draw_ia_prepare_outputs(draw, draw->pipeline.ia);
    draw_unfilled_prepare_outputs(draw, draw->pipeline.unfilled);
 }