tools/power turbostat: Fix warning upon failed /dev/cpu_dma_latency read

Previously a failed read of /dev/cpu_dma_latency erroneously complained
turbostat: capget(CAP_SYS_ADMIN) failed, try "# setcap cap_sys_admin=ep ./turbostat

This went unnoticed because this file is typically visible to root,
and turbostat was typically run as root.

Going forward, when a non-root user can run turbostat...
Complain about failed read access to this file only if --debug is used.
Signed-off-by: Len Brown <len.brown@intel.com>

tools/power/x86/turbostat/turbostat.c

@@ -5545,7 +5545,8 @@ void print_dev_latency(void)
 
 	fd = open(path, O_RDONLY);
 	if (fd < 0) {
-		warnx("capget(CAP_SYS_ADMIN) failed, try \"# setcap cap_sys_admin=ep %s\"", progname);
+		if (debug)
+			warnx("Read %s failed", path);
 		return;
 	}