Kconfig: fix single letter command in scripts/config

The one letter commands in scripts/config didn't work and always
printed usage. Fix this here.

Cc: erick@openchill.org
Reported-by: erick@openchill.org
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NMichal Marek <mmarek@suse.cz>

scripts/config

@@ -86,7 +86,7 @@ while [ "$1" != "" ] ; do
 		B=$ARG
 		shift 2
 		;;
-	--*)
+	-*)
 		checkarg "$1"
 		shift
 		;;