ASoC: fold pxa2xx-pcm into its only user, pxa2xx-ac97

Now that the PXA SSP bits are ported over to generic DMA, the pxa2xx-pcm
code only has a single user left. This patch folds the remaining bits into
its only user and removes the unnecessary glue layer along with its header
file.

The include dependency to linux/dma/pxa-dma.h is also gone now.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Mark Brown <broonie@kernel.org>