drm/gma500: drop drmP.h from header files

Drop use of drmp.h from all header files in drm/gma500.
Fix fallout in all files.
In some cases moved include lines and sorted them too.
With drmP.h removed from all header files it can now be removed from
each .c file without any further dependencies

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190519195526.3422-3-sam@ravnborg.org