drm: Split out drm_probe_helper.c from drm_crtc_helper.c

This is leftover stuff from my previous doc round which I kinda wanted
to do but didn't yet due to rebase hell.

The modeset helpers and the probing helpers a independent and e.g.
i915 uses the probing stuff but has its own modeset infrastructure. It
hence makes to split this up. While at it add a DOC: comment for the
probing libraray.

It would be rather neat to pull some of the DocBook documenting these
two helpers into in-line DOC: comments. But unfortunately kerneldoc
doesn't support markdown or something similar to make nice-looking
documentation, so the current state is better.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
index 0bb34ca..36a5feb 100644
--- a/include/drm/drm_crtc_helper.h
+++ b/include/drm/drm_crtc_helper.h
@@ -125,7 +125,6 @@
 	struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
 };
 
-extern int drm_helper_probe_single_connector_modes(struct drm_connector *connector, uint32_t maxX, uint32_t maxY);
 extern void drm_helper_disable_unused_functions(struct drm_device *dev);
 extern int drm_crtc_helper_set_config(struct drm_mode_set *set);
 extern bool drm_crtc_helper_set_mode(struct drm_crtc *crtc,
@@ -161,6 +160,11 @@
 }
 
 extern void drm_helper_resume_force_mode(struct drm_device *dev);
+
+/* drm_probe_helper.c */
+extern int drm_helper_probe_single_connector_modes(struct drm_connector
+						   *connector, uint32_t maxX,
+						   uint32_t maxY);
 extern void drm_kms_helper_poll_init(struct drm_device *dev);
 extern void drm_kms_helper_poll_fini(struct drm_device *dev);
 extern bool drm_helper_hpd_irq_event(struct drm_device *dev);