DMA: PL330: Add dma api driver

Add DMA Engine API driver for the PL330 DMAC.
This driver is supposed to be reusable by various
platforms that have one or more PL330 DMACs.
Atm, DMA_SLAVE and DMA_MEMCPY capabilities have been
implemented.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Reviewed-by: Linus Walleij <linus.walleij@stericsson.com>
[dan.j.williams@intel.com: missing slab.h and ->device_control() fixups]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>