avr32: at32ap700x: setup DMA for ABDAC in the machine code

This patch will adjust the setup the DMA controller for the Audio
Bistream DAC in the at32ap700x machine code. This setup matches the new
ALSA driver for the ABDAC.

Tested on ATSTK1006 + ATSTK1000.

This patch will setup the needed platform data for the Audio Bistream
DAC used by the Favr-32 board.

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
[haavard.skinnemoen@atmel.com: fold board code update]
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>