ASoC: fsl: Add dedicated DMA buffer size for each cpu dai

As the ssi is not the only cpu dai, there are esai, spdif, sai.
and imx_pcm_dma can be used by all of them. Especially ESAI need
a larger DMA buffer size. So Add dedicated DMA buffer for each cpu
dai.

Signed-off-by: Shengjiu Wang <shengjiu.wang@freescale.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Acked-by: Timur Tabi <timur@tabi.org>
Signed-off-by: Mark Brown <broonie@kernel.org>