cpupower: Add intel_pstate turbo boost support for Intel platforms

cpupower: Add intel_pstate turbo boost support for Intel platforms

On modern Intel platforms, the intel_pstate driver is commonly used and
it provides turbo boost control via
/sys/devices/system/cpu/intel_pstate/no_turbo.

However, cpupower doesn't handle this. it
1. shows turbo boost as "active" blindly for Intel platforms
2. controls turbo boost functionality via the generic
   /sys/devices/system/cpu/cpufreq/boost sysfs interface only.

Enhance the cpupower tool to ensure the "--boost" command works
seamlessly on Intel platforms with intel_pstate driver running.

Without this patch,
   $ echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
   1
   $ sudo cpupower frequency-info --boost
   analyzing CPU 21:
     boost state support:
       Supported: yes
       Active: yes
   $ sudo cpupower set --boost 0
   Error setting turbo-boost
   $ sudo cpupower set --boost 1
   Error setting turbo-boost

With this patch,
   $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
   0
   $ sudo cpupower set --boost 0
   $ sudo cpupower frequency-info --boost
   analyzing CPU 21:
     boost state support:
       Supported: yes
       Active: no
   $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
   1
   $ sudo cpupower set --boost 1
   $ sudo cpupower frequency-info --boost
   analyzing CPU 28:
     boost state support:
       Supported: yes
       Active: yes
   $ cat /sys/devices/system/cpu/intel_pstate/no_turbo
   0

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>