cpus: define QEMUTimerListNotifyCB for QEMU system emulation

There is no change for now, because the callback just invokes
qemu_notify_event.

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/util/main-loop.c b/util/main-loop.c
index 7efc229..4534c89 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -144,7 +144,7 @@
     GSource *src;
     Error *local_error = NULL;
 
-    init_clocks();
+    init_clocks(qemu_timer_notify_cb);
 
     ret = qemu_signal_init();
     if (ret) {