mtd: denali: convert to generic DMA API

Rather than using the PCI specific DMA API, convert to the generic
DMA API so that we can use the Denali NAND controller on other bus
types.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>