drm/edid: Move HDMI_IDENTIFIER to hdmi.h

We'll need the HDMI OUI for the HDMI vendor infoframe data, so let's
move the DRM one to hdmi.h, might as well use the hdmi header to store
some hdmi defines.

(Note that, in fact, infoframes are part of the CEA-861 standard, and
only the HDMI vendor specific infoframe is special to HDMI, but
details..)

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dave Airlie <airlied@gmail.com>