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>

include/sysemu/cpus.h

@@ -22,6 +22,7 @@ void dump_drift_info(FILE *f, fprintf_function cpu_fprintf);
 
 /* Unblock cpu */
 void qemu_cpu_kick_self(void);
+void qemu_timer_notify_cb(void *opaque, QEMUClockType type);
 
 void cpu_synchronize_all_states(void);
 void cpu_synchronize_all_post_reset(void);