kbuild: print usage with no arguments in scripts/config

Requested by Sam.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/config

@@ -60,6 +60,10 @@ else
 	FN=.config
 fi
 
+if [ "$1" = "" ] ; then
+	usage
+fi
+
 while [ "$1" != "" ] ; do
 	CMD="$1"
 	shift