dmaengine: pl330: Merge dma_pl330_dmac and pl330_dmac structs

Both the dma_pl330_dmac and the pl330_dmac struct have the same lifetime and the
separation of them is a relict of this having been two different drivers in the
past. Merging them into one struct makes the code a bit simpler as it for
example allows to remove the pointers going back and forth between the two
structs.

While we are at it also directly embed the pl330_info struct into the
pl330_dmac struct as this allows to remove some more redundant fields.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>