drm/panel-edp: Split eDP panels out of panel-simple

The panel-simple driver handles way too much. Let's start trying to
get a handle on it by splitting out the eDP panels. This patch does
this:

1. Start by copying simple-panel verbatim over to a new driver,
   simple-panel-edp.
2. Rename "panel_simple" to "panel_edp" in the new driver.
3. Keep only panels marked with `DRM_MODE_CONNECTOR_eDP` in the new
   driver. Remove those panels from the old driver.
4. Remove all recent "DP AUX bus" stuff from the old driver. The DP
   AUX bus is only possible on DP panels.
5. Remove all DSI / MIPI related functions from the new driver.
6. Remove bus_format / bus_flags from eDP driver. These things don't
   seem to make any sense for eDP panels so let's stop filling in made
   up stuff.

In the end we end up with a bunch of duplicated code for now. Future
patches will try to address _some_ of this duplicated code though some
of it will be unavoidable.

NOTE: This may not actually move all eDP panels over to the new driver
since not all panels were properly marked with
`DRM_MODE_CONNECTOR_eDP`. A future patch will attempt to move wayward
panels I could identify but even so there may be some missed.

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914132020.v5.7.I0a2f75bb822d17ce06f5b147734764eeb0c3e3df@changeid