usertools/hugepages: show usage if no action specified

Previously, the script was doing nothing if no argument was provided.

If neither show, mount/unmount, clear/reserve are specified,
it is assumed that the user does not know how to use the script.
So the usage and an error message are printed.
The exit code will be non-zero.
The user will understand something is wrong,
and can recall the script with the option -h to get more information.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: David Marchand <david.marchand@redhat.com>

usertools/dpdk-hugepages.py

@@ -272,6 +272,9 @@ To a complete setup of with 2 Gigabyte of 1G huge pages:
         args.reserve = args.setup
         args.mount = True
 
+    if not (args.show or args.mount or args.unmount or args.clear or args.reserve):
+        parser.error("no action specified")
+
     if args.pagesize:
         pagesize_kb = get_memsize(args.pagesize)
     else: