tools/power turbostat: return the exit status of a command

turbostat failed to return a non-zero exit status even though the
supplied command (turbostat <command>) failed.  Currently when turbostat
forks a command it returns zero instead of the actual exit status of the
command.  Modify the code to return the exit status.

Signed-off-by: David Arcari <darcari@redhat.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

tools/power/x86/turbostat/turbostat.c

@@ -5077,6 +5077,9 @@ int fork_it(char **argv)
 		signal(SIGQUIT, SIG_IGN);
 		if (waitpid(child_pid, &status, 0) == -1)
 			err(status, "waitpid");
+
+		if (WIFEXITED(status))
+			status = WEXITSTATUS(status);
 	}
 	/*
 	 * n.b. fork_it() does not check for errors from for_all_cpus()