cpufreq: Exit governor when failed to start old governor

Detect the result of starting old governor in cpufreq_set_policy(). If it
fails, exit the governor and clear policy->governor.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Link: https://patch.msgid.link/20250709104145.2348017-5-zhenglifeng1@huawei.com


Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>