small powerpc DMA fixes and cleanups

[Christoph Hellwig]

Hi all,

this series has a few smaller fixes and cleanups for the powerpc
DMA code.

The biggest changes are related to the not cache coherent DMA
support, which as far as I can tell was not consistent in its
cache maintainance operations.  Also the AMCC ppc44x crypto
driver looks like it was affected by that (or otherwise just
odd) and used a helper internal to the powerpc DMA code to
work around that fact.  I've added Christian Lamparter who has
been trying to beat that driver into shape in the last years
for that reason.