tools/power/turbostat: Move process to root cgroup

When available CPUs are reduced via cgroup cpuset controller, turbostat
will exit with errors (For example):
	get_counters: Could not migrate to CPU 0
	turbostat: re-initialized with num_cpus 20
	get_counters: Could not migrate to CPU 0
	turbostat: re-initialized with num_cpus 20

Move the turbostat to root cgroup, which has every CPU.

Writing the value 0 to a cgroup.procs file causes the writing
process to be moved to the corresponding cgroup.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Tested-by: Zhang Rui <rui.zhang@intel.com>

tools/power/x86/turbostat/turbostat.c

@@ -6666,6 +6666,19 @@ void cmdline(int argc, char **argv)
 
 int main(int argc, char **argv)
 {
+	int fd, ret;
+
+	fd = open("/sys/fs/cgroup/cgroup.procs", O_WRONLY);
+	if (fd < 0)
+		goto skip_cgroup_setting;
+
+	ret = write(fd, "0\n", 2);
+	if (ret == -1)
+		perror("Can't update cgroup\n");
+
+	close(fd);
+
+skip_cgroup_setting:
 	outf = stderr;
 	cmdline(argc, argv);