v4l2transform: fix cdata caps leaks
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().

pexip/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good