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().
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().