dmaengine: ioatdma: move dma prep functions to single location

Move all DMA descriptor prepping functions to prep.c file. Fixup all
broken bits caused by the move.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
6 files changed