video/hdmi: Hook the HDMI vendor infoframe with the generic _pack()
With this last bit, hdmi_infoframe_pack() is now able to pack any
infoframe we support.
At the same time, because it's impractical to make two commits out of
this, we get rid of the version that encourages the open coding of the
vendor infoframe packing. We can do so because the only user of this API
has been ported in: