qom: cpu: destroy work_mutex in cpu_common_finalize

Commit 376692b9dc6(cpus: protect work list with work_mutex)
initialize a work_mutex in cpu_common_initfn, however forget
to destroy it. This will cause resource leak when hotunplug cpu
or hotplug cpu fails.

Signed-off-by: Li Qiang <liq3ea@163.com>
Message-Id: <20190102074114.26988-1-liq3ea@163.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qom/cpu.c

@@ -380,6 +380,9 @@ static void cpu_common_initfn(Object *obj)
 
 static void cpu_common_finalize(Object *obj)
 {
+    CPUState *cpu = CPU(obj);
+
+    qemu_mutex_destroy(&cpu->work_mutex);
 }
 
 static int64_t cpu_common_get_arch_id(CPUState *cpu)