v4l2transform: fix cdata caps leaks

The cdata structure was freed but not its caps.
It was already done in gst_v4l2_video_dec_subclass_init() and
gst_v4l2_video_enc_subclass_init().

sys/v4l2/gstv4l2transform.c

@@ -1159,6 +1159,8 @@ gst_v4l2_transform_subclass_init (gpointer g_class, gpointer data)
       gst_pad_template_new ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
           cdata->src_caps));
 
+  gst_caps_unref (cdata->sink_caps);
+  gst_caps_unref (cdata->src_caps);
   g_free (cdata);
 }