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 <sam@ravnborg.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190126122527.11647-5-sam@ravnborg.org

drivers/gpu/drm/drm_damage_helper.c

@@ -32,6 +32,7 @@
 
 #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

@@ -22,8 +22,10 @@
 
 #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>
 
 /**