m32r: add simple dma

Some builds of m32r were failing as it tried to build few drivers which
needed dma but m32r is not having dma support.  Objections were raised
when it was tried to make those drivers depend on HAS_DMA.  So the next
best thing is to add dma support to m32r.  dma_noop is a very simple dma
with 1:1 memory mapping.

Link: http://lkml.kernel.org/r/1475949198-31623-1-git-send-email-sudipm.mukherjee@gmail.com


Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>