tracing/fastboot: put error message on stderr

Since this scripts output is usually redirected, put error messages
on standard error and exit with error code if no data is found.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Acked-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

scripts/bootgraph.pl

@@ -78,11 +78,13 @@ while (<>) {
 }
 
 if ($count == 0) {
-	print "No data found in the dmesg. Make sure that 'printk.time=1' and\n";
-	print "'initcall_debug' are passed on the kernel command line.\n\n";
-	print "Usage: \n";
-	print "      dmesg | perl scripts/bootgraph.pl > output.svg\n\n";
-	exit;
+    print STDERR <<END;
+No data found in the dmesg. Make sure that 'printk.time=1' and
+'initcall_debug' are passed on the kernel command line.
+Usage:
+      dmesg | perl scripts/bootgraph.pl > output.svg
+END
+    exit 1;
 }
 
 print "<?xml version=\"1.0\" standalone=\"no\"?> \n";