usb_scan_devices: fix output with no devices

We should check the return of usb_new_device() so that if no USB device is
found, we print out the right message rather than always saying "new usb
device found".

Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Remy Bohmer <linux@bohmer.net>

common/usb.c

@@ -939,8 +939,10 @@ void usb_scan_devices(void)
 	dev_index = 0;
 	/* device 0 is always present (root hub, so let it analyze) */
 	dev = usb_alloc_new_device();
-	usb_new_device(dev);
-	printf("%d USB Device(s) found\n", dev_index);
+	if (usb_new_device(dev))
+		printf("No USB Device found\n");
+	else
+		printf("%d USB Device(s) found\n", dev_index);
 	/* insert "driver" if possible */
 #ifdef CONFIG_USB_KEYBOARD
 	drv_usb_kbd_init();