MIPS: Fix poweroff failure when HOTPLUG_CPU configured.

When poweroff machine, kernel_power_off() call disable_nonboot_cpus().
And if we have HOTPLUG_CPU configured, disable_nonboot_cpus() is not an
empty function but attempt to actually disable the nonboot cpus. Since
system state is SYSTEM_POWER_OFF, play_dead() won't be called and thus
disable_nonboot_cpus() hangs. Therefore, we make this patch to avoid
poweroff failure.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Hongliang Tao <taohl@lemote.com>
Signed-off-by: Hua Yan <yanh@lemote.com>
Cc: Yong Zhang <yong.zhang@windriver.com>
Cc: stable@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/4211/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/process.c

@@ -72,9 +72,7 @@ void __noreturn cpu_idle(void)
 			}
 		}
 #ifdef CONFIG_HOTPLUG_CPU
-		if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
-		    (system_state == SYSTEM_RUNNING ||
-		     system_state == SYSTEM_BOOTING))
+		if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map))
 			play_dead();
 #endif
 		rcu_idle_exit();