drm: Move dma functions into drm_legacy.h

Also drop the unneeded EXPORT_SYMBOL and sprinkle drm_legacy_ prefixes
where missing.

v2: Drop the confusing _core_ and drop extern, both suggested by
David.

Cc: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_fops.c

@@ -404,7 +404,7 @@ int drm_release(struct inode *inode, struct file *filp)
 		drm_master_release(dev, filp);
 
 	if (drm_core_check_feature(dev, DRIVER_HAVE_DMA))
-		drm_core_reclaim_buffers(dev, file_priv);
+		drm_legacy_reclaim_buffers(dev, file_priv);
 
 	drm_events_release(file_priv);