drm/exynos: make dvi the default mode

DVI is the safest mode for compatibility.
If the display is a HDMI one it will be fixed below.
This ensure that even if the EDID is failed it will fall to DVI mode
defconfigs: enable DRM edid parsing and make the edid blobs built-in
firmware: add edid firmwares
drm/exynos: fix logic error on where dvi mode should be configured
Documentation/edid: add the 720p edid example file