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>

stubs/cpu-get-icount.c

@@ -2,6 +2,7 @@
 #include "qemu-common.h"
 #include "qemu/timer.h"
 #include "sysemu/cpus.h"
+#include "qemu/main-loop.h"
 
 int use_icount;
 
@@ -9,3 +10,8 @@ int64_t cpu_get_icount(void)
 {
     abort();
 }
+
+void qemu_timer_notify_cb(void *opaque, QEMUClockType type)
+{
+    qemu_notify_event();
+}