radeonsi: restore si_emit_cache_flush call at the end of IBs

Fixes: 918b798668 "radeonsi: make sure CP DMA is idle at the end of IBs"

src/gallium/drivers/radeonsi/si_gfx_cs.c

@@ -116,6 +116,8 @@ void si_flush_gfx_cs(struct si_context *ctx, unsigned flags,
 	if (ctx->chip_class >= CIK)
 		si_cp_dma_wait_for_idle(ctx);
 
+	si_emit_cache_flush(ctx);
+
 	if (ctx->current_saved_cs) {
 		si_trace_emit(ctx);
 		si_log_hw_flush(ctx);