st/mesa: release tgsi tokens for shader states

Since we are using st_common_variant while creating variant for vertext
program, we can release tokens created in st_create_vp_variant which
are already stored in respective states.
This fix memory leak found with piglit tests

Fixes bc99b22a30 ('st/mesa: use a separate VS variant for the draw module')

Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>

src/mesa/state_tracker/st_program.c

@@ -694,6 +694,10 @@ st_create_vp_variant(struct st_context *st,
    else
       vpv->base.driver_shader = pipe->create_vs_state(pipe, &state);
 
+   if (state.tokens) {
+      tgsi_free_tokens(state.tokens);
+   }
+
    return vpv;
 }