drm/sis: drop drmP.h use

Drop use of the deprecated drmP.h header.
Repalced with relevant header files and sorted header files in all files
touched.

Replaced DRM_{READ,WRITE} to avoid the drm_os_linux header.

Build tested with allyesconfig, allmodconfig on various architectures.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Link: https://patchwork.freedesktop.org/patch/msgid/20190605135539.12940-2-sam@ravnborg.org