cpupower: Do not change the frequency of offline cpu

Check if the cpu is online before changing the frequency/governor of
the cpu.

Reported-by: Pavaman Subramaniyam <pavsubra@linux.vnet.ibm.com>
Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: Thomas Renninger <trenn@suse.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

tools/power/cpupower/utils/cpufreq-set.c

@@ -17,6 +17,7 @@
 
 #include "cpufreq.h"
 #include "helpers/helpers.h"
+#include "helpers/sysfs.h"
 
 #define NORM_FREQ_LEN 32
 
@@ -318,6 +319,9 @@ int cmd_freq_set(int argc, char **argv)
 		    cpufreq_cpu_exists(cpu))
 			continue;
 
+		if (sysfs_is_cpu_online(cpu) != 1)
+			continue;
+
 		printf(_("Setting cpu: %d\n"), cpu);
 		ret = do_one_cpu(cpu, &new_pol, freq, policychange);
 		if (ret) {