drm: prepare for drmP.h removal from drm_modeset_helper.h

The use of drmP.h is discouraged and removal of it from
drm_modeset_helper.h caused drm/ to fail to build.

This patch introduce the necessary fixes to prepare for the
drmP.h removal from drm_modeset_helper.h.

Build tested on x86, arm, alpha, ia64 allmodconfig/allyesconfig.

Signed-off-by: Sam Ravnborg <[e-mail]>
Cc: Maarten Lankhorst <[e-mail]>
Cc: Maxime Ripard <[e-mail]>
Cc: Sean Paul <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_damage_helper.c

···
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_damage_helper.h>
+#include <drm/drm_device.h>
 
 /**
  * DOC: overview

drivers/gpu/drm/drm_modeset_helper.c

···
 
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_fb_helper.h>
+#include <drm/drm_fourcc.h>
 #include <drm/drm_modeset_helper.h>
 #include <drm/drm_plane_helper.h>
+#include <drm/drm_print.h>
 #include <drm/drm_probe_helper.h>
 
 /**