avr32: at32ap700x: specify DMA src and dst masters

Now that the dw_dmac DMA driver supports configurable source and
destination masters we need to specify which ones to use. This was
previously hardcoded to 0 and 1 respectively in the driver.

Acked-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>