drm/doc: Include new drm_blend.c

There's not much point in kerneldoc if it's not included:
- It won't show up in the pretty html pages.
- The comments itself won't get parsed, which means 0day won't pick up
  changes, resulting in stale docs fast.

Also, uapi really should be core, not helpers, so move drm_blend.c to
that. That also means that the zpos normilize function loses it's
helper status (and we might as well call it always). For that,
EXPORT_SYMBOL. Just spotted while integrating docs and noticing that
one was missing.

With sphinx there's really no excuse any more to not build the docs
and make sure it's all nice!

$ make DOCBOOKS="" htmldocs

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471034937-651-15-git-send-email-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
index f3c0942..0813b7e 100644
--- a/drivers/gpu/drm/drm_blend.c
+++ b/drivers/gpu/drm/drm_blend.c
@@ -193,8 +193,7 @@
 }
 
 /**
- * drm_atomic_helper_normalize_zpos - calculate normalized zpos values for all
- *				      crtcs
+ * drm_atomic_normalize_zpos - calculate normalized zpos values for all crtcs
  * @dev: DRM device
  * @state: atomic state of DRM device
  *
@@ -205,8 +204,8 @@
  * RETURNS
  * Zero for success or -errno
  */
-int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
-				     struct drm_atomic_state *state)
+int drm_atomic_normalize_zpos(struct drm_device *dev,
+			      struct drm_atomic_state *state)
 {
 	struct drm_crtc *crtc;
 	struct drm_crtc_state *crtc_state;
@@ -236,3 +235,4 @@
 	}
 	return 0;
 }
+EXPORT_SYMBOL(drm_atomic_normalize_zpos);