Revert "st/mesa: Always recalculate invalid index bounds."

This reverts commit 50876ddaaf.

Per ML discussion.

src/mesa/state_tracker/st_draw.c

@@ -542,9 +542,9 @@ st_draw_vbo(GLcontext *ctx,
    assert(ctx->NewState == 0x0);
 
    /* Gallium probably doesn't want this in some cases. */
-   if (index_bounds_valid != GL_TRUE) {
-      vbo_get_minmax_index(ctx, prims, ib, &min_index, &max_index);
-   }
+   if (!index_bounds_valid)
+      if (!vbo_all_varyings_in_vbos(arrays))
+	 vbo_get_minmax_index(ctx, prims, ib, &min_index, &max_index);
 
    /* sanity check for pointer arithmetic below */
    assert(sizeof(arrays[0]->Ptr[0]) == 1);