Add CPU MHz as the value for "node_cpu_info" metric

For CPUs which don't have an available (or insertable) cpufreq driver,
the /proc/cpuinfo file can sometimes have accurate CPU core frequency
measurements. This change replaces the constant value of "1" for the
"node_cpu_info" metric with the parsed CPU MHz value from
/proc/cpuinfo for each core.

Signed-off-by: John Kordich <jkordich@gmail.com>

collector/cpu_linux.go

@@ -184,7 +184,7 @@ func (c *cpuCollector) updateInfo(ch chan<- prometheus.Metric) error {
 	for _, cpu := range info {
 		ch <- prometheus.MustNewConstMetric(c.cpuInfo,
 			prometheus.GaugeValue,
-			1,
+			cpu.CPUMHz,
 			cpu.PhysicalID,
 			cpu.CoreID,
 			strconv.Itoa(int(cpu.Processor)),