soc: sunxi: Deal with the MBUS DMA offsets in a central place

So far most of the drivers with the MBUS quirks had to duplicate the
code to deal with DT compatibility and enforcing the DMA offsets.

Let's move for a more maintainable solution by putting everything in a
notifier that would take care of setting up the DMA offsets for all the
MBUS devices.

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>