v4l2object: fix capture with bayer formats other than bggr
v4l2object: fix capture with bayer formats other than bggr

gst_v4l2_object_get_caps_info() always return V4L2_PIX_FMT_SBGGR8
for all bayer formats. This is obviously broken if the device use
another ordering. Fix this by properly reading the format parameter.

https://bugzilla.gnome.org/show_bug.cgi?id=763318

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