The DSI version of the panel behaved instable and close
scrutiny of the vendor driver from the Samsung
GT-S8190 shows a different initialization sequence for
the DSI mode panel than the DPI mode panel.

Make the initialization depend on whether we are in
DSI or DPI mode and handle the differences.

After this the panel on the GT-I8190 becomes much more
stable.

Also spell out some more custom DCS commands found in
the vendor source code to cut down a bit on magic
where we can.

Fixes: f0aee45f ("drm/panel: s6e63m0: Fix init sequence")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Stephan Gerhold <stephan@gerhold.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20201205122229.1952980-1-linus.walleij@linaro.org