Fixes thread compare in vkr_ring_stop by using thrd_equal

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Part-of: <https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/713>

src/venus/vkr_ring.c

@@ -351,7 +351,7 @@ bool
 vkr_ring_stop(struct vkr_ring *ring)
 {
    mtx_lock(&ring->mutex);
-   if (ring->thread == thrd_current()) {
+   if (thrd_equal(ring->thread, thrd_current())) {
       mtx_unlock(&ring->mutex);
       return false;
    }