cpuidle: fix return type err in haltpoll_switch_governor

euleros inclusion
category: bugfix
bugzilla: NA
CVE: NA

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while CONFIG_CPU_IDLE is disabled, the haltpoll_switch_governor function
should not return int type result,which will cause build err.

Fixes: 97c22788 ("cpuidle: fix container_of err in cpuidle_device and cpuidle_driver")
Signed-off-by: Jiajun Chen <chenjiajun8@huawei.com>
Reviewed-by: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>