ASoC: ux500_pcm: Stop pretending that we support varying address widths

The Slave Config's addr_width attribute is populated by data_width of
dma_cfg, which in turn is derived from dma_params' data_size attribute
and that comes from the slot_width which is always 16 bits (2 Bytes).
We're cutting out the middle man here and just setting the DMA Slave
Config directly.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>