v4l2: Let gstv4l2object recognize V4L2 bt601 colorimetry again
V4L2 makes no difference between the BT.601 and BT.709 transfer functions, but GStreamer does since 1.18.
Adapt gst_v4l2_object_get_colorspace() and gst_v4l2_object_set_format_full().
Edited by Tim-Philipp Müller