asahi: Sync when beginning a query

Otherwise batch->writer might be non-null. Fixes Piglit occlusion_query_conform
(which I think regressed when we added proper syncing).

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24847>

src/gallium/drivers/asahi/agx_query.c

@@ -81,6 +81,7 @@ agx_begin_query(struct pipe_context *pctx, struct pipe_query *pquery)
     */
    if (query->writer) {
       agx_flush_batch_for_reason(ctx, query->writer, "Query overwritten");
+      agx_sync_batch_for_reason(ctx, query->writer, "Query overwrriten");
    }
 
    assert(query->writer == NULL);