drm/vkms: drop use of drmP.h

Drop use of the deprecated drmP.h header.
Replace it with the necessary includes in the individual .c files.
The header files was self-contained, and extra includes were not added
there.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Acked-by: Emil Velikov <emil.velikov@collabora.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Link: https://patchwork.freedesktop.org/patch/msgid/20190630061922.7254-13-sam@ravnborg.org

drivers/gpu/drm/vkms/vkms_plane.c

@@ -1,10 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0+
 
-#include "vkms_drv.h"
-#include <drm/drm_plane_helper.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_fourcc.h>
 #include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_plane_helper.h>
+
+#include "vkms_drv.h"
 
 static const u32 vkms_formats[] = {
 	DRM_FORMAT_XRGB8888,