uvc: fix init_formats function

The return value of scandir is used in init_frames to iterate over
the elements. The iteration is done over nmb not ret. So this patch
is fixing this to fill the right variable.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

src/function/uvc.c

@@ -173,8 +173,8 @@ int init_frames(struct usbg_f_uvc *uvc, int j)
 		return ret;
 	}
 
-	ret = scandir(fpath, &dent, frame_select, frame_sort);
-	if (ret < 0) {
+	nmb = scandir(fpath, &dent, frame_select, frame_sort);
+	if (nmb < 0) {
 		ret = usbg_translate_error(errno);
 		return ret;
 	}