Changes the way the primary mode is handled:
- Remove it from platform_data since it doesn't belong there.
- Add a new mode enum for use with s_routing.
- Collapse the two HDMI modes into one HDMI mode: when setting up the
timings manually we do not need to select HDMI_COMP mode. That's only
needed when selecting a preset.
This patch prepares for the next step where we switch to using the presets
where available.