dont parse uninitialized memory

Reference: /n/atom/patch/applied/usbkbbaddesc
Date: Fri Mar 28 16:33:21 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/usb/kb/kb.c	Fri Mar 28 16:33:16 2014
+++ /sys/src/cmd/usb/kb/kb.c	Fri Mar 28 16:33:17 2014
@@ -762,7 +762,6 @@
 	d->free = freekdev;
 	kd->in = in;
 	kd->dev = d;
-	res = -1;
 	kd->ep = openep(d, ep->id);
 	if(kd->ep == nil){
 		fprint(2, "kb: %s: workep: openep %d: %r\n", d->dir, ep->id);
@@ -782,10 +781,12 @@
 				kd->idle = Dwcidle;
 		}
 	}
-	if(!kd->bootp)
-		res= setfirstconfig(kd, ep->id, desc, sizeof desc);
-	if(res > 0)
-		res = parsereportdesc(&kd->templ, desc, sizeof desc);
+	res = -1;
+	if(!kd->bootp){
+		n = setfirstconfig(kd, ep->id, desc, sizeof desc);
+		if(n > 0)
+			res = parsereportdesc(&kd->templ, desc, n);
+	}
 	/* if we could not set the first config, we give up */
 	if(kd->bootp || res < 0){
 		kd->bootp = 1;