Move vm_state_notify() prototype from cpus.h to sysemu.h

It's where all the state handling functions prototypes are located.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

cpus.h

@@ -15,7 +15,6 @@ void cpu_synchronize_all_post_init(void);
 /* vl.c */
 extern int smp_cores;
 extern int smp_threads;
-void vm_state_notify(int running, int reason);
 bool cpu_exec_all(void);
 void set_numa_modes(void);
 void set_cpu_log(const char *optarg);

sysemu.h

@@ -23,6 +23,7 @@ typedef void VMChangeStateHandler(void *opaque, int running, int reason);
 VMChangeStateEntry *qemu_add_vm_change_state_handler(VMChangeStateHandler *cb,
                                                      void *opaque);
 void qemu_del_vm_change_state_handler(VMChangeStateEntry *e);
+void vm_state_notify(int running, int reason);
 
 #define VMSTOP_USER      0
 #define VMSTOP_DEBUG     1