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: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/config b/scripts/config
index 608d7fd..dfd4732 100755
--- a/scripts/config
+++ b/scripts/config
@@ -86,7 +86,7 @@
 		B=$ARG
 		shift 2
 		;;
-	--*)
+	-*)
 		checkarg "$1"
 		shift
 		;;