drm/kms-helpers: Extract drm_modeset_helper.[hc]

While reviewing docs I spotted that we have a few functions that
really just don't fit into their containing helper library section.
Extract them and shovel them all into a new library for random one-off
aux stuff.

v2: Remove wrongly added files for real.

Cc: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471034937-651-3-git-send-email-daniel.vetter@ffwll.ch
diff --git a/include/drm/drm_plane_helper.h b/include/drm/drm_plane_helper.h
index fbc8ecb..c189596 100644
--- a/include/drm/drm_plane_helper.h
+++ b/include/drm/drm_plane_helper.h
@@ -27,6 +27,7 @@
 #include <drm/drm_rect.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_modeset_helper.h>
 
 /*
  * Drivers that don't allow primary plane scaling may pass this macro in place
@@ -37,9 +38,6 @@
  */
 #define DRM_PLANE_HELPER_NO_SCALING (1<<16)
 
-int drm_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
-		  const struct drm_crtc_funcs *funcs);
-
 int drm_plane_helper_check_state(struct drm_plane_state *state,
 				 const struct drm_rect *clip,
 				 int min_scale, int max_scale,