st/mesa: disable L3 thread pinning

This implementation can have massive drawbacks.

Cc: 18.3 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Edmondo Tommasina <edmondo.tommasina@gmail.com>

src/mesa/state_tracker/st_manager.c

@@ -1072,15 +1072,6 @@ st_api_make_current(struct st_api *stapi, struct st_context_iface *stctxi,
        * of the referenced drawables no longer exist.
        */
       st_framebuffers_purge(st);
-
-      /* Notify the driver that the context thread may have been changed.
-       * This should pin all driver threads to a specific L3 cache for optimal
-       * performance on AMD Zen CPUs.
-       */
-      struct glthread_state *glthread = st->ctx->GLThread;
-      thrd_t *upper_thread = glthread ? &glthread->queue.threads[0] : NULL;
-
-      util_context_thread_changed(st->pipe, upper_thread);
    }
    else {
       ret = _mesa_make_current(NULL, NULL, NULL);