fio2gnuplot: Fixing help message

Some options were missing on the main description.
diff --git a/tools/plot/fio2gnuplot.py b/tools/plot/fio2gnuplot.py
index e749c51..203908a 100755
--- a/tools/plot/fio2gnuplot.py
+++ b/tools/plot/fio2gnuplot.py
@@ -319,7 +319,7 @@
 		sys.exit(1);
 
 def print_help():
-    print 'fio2gnuplot.py -ghbio -t <title> -o <outputfile> -p <pattern>'
+    print 'fio2gnuplot.py -ghbiod -t <title> -o <outputfile> -p <pattern> -G <type>'
     print
     print '-h --help                           : Print this help'
     print '-p <pattern> or --pattern <pattern> : A pattern in regexp to select fio input files'