drm/panel: atna33xc20: Introduce the Samsung ATNA33XC20 panel

The Samsung ATNA33XC20 panel is an AMOLED eDP panel that has backlight
control over the DP AUX channel.

This panel is _almost_ able to be controlled in a "simple" way (and it
originally was implemented in panel-simple.c), but it's really
impossible to get the backlight semantics right there without adding
wacky special-case code to panel-simple. Let's give up and clone the
parts of panel-simple that we need and implement the power sequence
that this panel needs.

NOTE: we'll still leave the devicetree bindings alone. Even though the
power-sequencing is non-standard the bindings are still "simple".

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210730084534.v2.6.I3a2900080f8749d2bb4baf49ca902db4b0e1df7d@changeid