Drop use of the deprecated drmP.h header file.

While touching the list of include files:
- Divide include files in blocks of linux/* drm/* etc.
- Sort individual blocks of include files
- Remove duplicated header file

v2:
- Be consistent in the order of the include blocks (Laurent)
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Peter Senna Tschudin <peter.senna@gmail.com>
Cc: Martin Donnelly <martin.donnelly@ge.com>
Cc: Martyn Welch <martyn.welch@collabora.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190519183636.19588-1-sam@ravnborg.org