ASoC: atmel-pcm-pdc: merge atmel-pcm back in

atmel-pcm.c was split into two files to create a generic framework for both PDC
and DMA.

atmel-pcm-dma.c is using the generic dmaengine framework since 95e0e07e
(ASoC: atmel-pcm: use generic dmaengine framework).

Merge atmel-pcm.c in atmel-pcm-pdc.c as this is now the only user.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>