tools/power/x86/intel-speed-select: Output success/failed for command output

Command output has confusing data, returning "0" on success.  For example

|# ./intel-speed-select -c 14 turbo-freq enable
Intel(R) Speed Select Technology
Executing on CPU model:106[0x6a]
 package-1
   die-0
     cpu-14
       turbo-freq
         enable:0

To avoid confusion change the command output to 'success' or 'failed'.

v2: Remove help output line.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: David Arcari <darcari@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>