drm/edid: Add flag to drm_display_info to identify HDMI sinks

The drm_display_info structure contains many fields related to HDMI
sinks, but none that identifies if a sink compliant with CEA-861 (EDID)
shall be treated as an HDMI sink or a DVI sink. Add such a flag, and
populate it according to section 8.3.3 ("DVI/HDMI Device
Discrimination") of the HDMI v1.3 specification.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200226112514.12455-4-laurent.pinchart@ideasonboard.com