perf pmu-events x86: Use CPU_CLK_UNHALTED.THREAD in Kernel_Utilization metric

perf pmu-events x86: Use CPU_CLK_UNHALTED.THREAD in Kernel_Utilization metric

The kernel utilization metric does multiplexing currently and is somewhat
unreliable. The problem is that it uses two instances of the fixed counter,
and the kernel has to multipleplex which causes errors. So should use
CPU_CLK_UNHALTED.THREAD instead.

Before:

  # perf stat -M Kernel_Utilization -- sleep 1

  Performance counter stats for 'sleep 1':

          1,419,425      cpu_clk_unhalted.ref_tsc:k
      <not counted>      cpu_clk_unhalted.ref_tsc	(0.00%)

After:

  # perf stat -M Kernel_Utilization -- sleep 1

  Performance counter stats for 'sleep 1':

            746,688      cpu_clk_unhalted.thread:k #      0.7 Kernel_Utilization
          1,088,348      cpu_clk_unhalted.thread

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200309013125.7559-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>