drm/doc: Task to rename CMA helpers

I'm kinda fed up explaining why the have a confusing name :-)

v2: Fix typo that Eric Engestrom spotted.

Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129132153.28844-1-daniel.vetter@ffwll.ch

Documentation/gpu/todo.rst

@@ -262,6 +262,16 @@ As a reference, take a look at the conversions already completed in drm core.
 
 Contact: Sean Paul, respective driver maintainers
 
+Rename CMA helpers to DMA helpers
+---------------------------------
+
+CMA (standing for contiguous memory allocator) is really a bit an accident of
+what these were used for first, a much better name would be DMA helpers. In the
+text these should even be called coherent DMA memory helpers (so maybe CDM, but
+no one knows what that means) since underneath they just use dma_alloc_coherent.
+
+Contact: Laurent Pinchart, Daniel Vetter
+
 Core refactorings
 =================