drm/panel: drop drmP.h usage

Drop use of the deprecated drmP.h header file.

While touching the list of include files:
- Divide include files in blocks of linux/* video/* drm/* etc.
  Be consistent in the order of the blocks
- Sort individual blocks of include files

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Stefan Mavrodiev <stefan@olimex.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190526180532.1641-3-sam@ravnborg.org