cpufreq: CPPC: Add support for autonomous selection

Add sysfs interfaces for CPPC autonomous selection in the cppc_cpufreq
driver.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Reviewed-by: Sumit Gupta <sumitg@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20250507031941.2812701-1-zhenglifeng1@huawei.com


[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>