v4l2object: refactor gst_v4l2_object_get_colorspace to take a v4l2_format parameter
v4l2object: refactor gst_v4l2_object_get_colorspace to take a v4l2_format parameter

Move the extraction of colorimetry parameters from struct v4l2_format and the
setting of the identity matrix for RGB formats into the function to avoid code
duplication.

https://bugzilla.gnome.org/show_bug.cgi?id=766383

StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,pexip/gst-plugins-good,hizukiayaka/gst-plugins-good,pexip/gst-plugins-good,StreamUtils/gst-plugins-good,StreamUtils/gst-plugins-good,GrokImageCompression/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,GStreamer/gst-plugins-good,stfl/gst-plugins-good,pexip/gst-plugins-good,stfl/gst-plugins-good,hizukiayaka/gst-plugins-good,GrokImageCompression/gst-plugins-good,hizukiayaka/gst-plugins-good,pexip/gst-plugins-good,GrokImageCompression/gst-plugins-good,hizukiayaka/gst-plugins-good,stfl/gst-plugins-good,stfl/gst-plugins-good,GrokImageCompression/gst-plugins-good