drm/sun4i: drop use of drmP.h

Drop use of the deprecated drmP.h header file.

While touching the list of include file, use the typical order of the
blocks:
\#include <linux/*>

\#include <video/*>

\#include <drm/*>

\#include ""

Within each block, sort the files.
Include necessary files to fix build after the drmP.h removal.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Emil Velikov <emil.velikov@collabora.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190716064220.18157-6-sam@ravnborg.org