Blackfin: standardize DMAC traffic control MMRs & MDMA MMRs

Use the same naming convention for DMA traffic MMRs (most were legacy
anyways) so we can avoid useless ifdef trees.

Same goes for MDMA names -- this actually allows us to undo a bunch of
ifdef redirects that existed for this purpose alone.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>