davinci: da8xx/omap-l1x: add platform device for davinci-pcm-audio

After the multi-component commit f0fba2ad (ASoC: multi-component - ASoC
Multi-Component Support) for ASoC, we need to register the platform
device for davinci-pcm-audio.

This patch and patch at [1] are required for audio to work on
DA850/OMAP-L138.

[1] https://patchwork.kernel.org/patch/495211/



Signed-off-by: Rajashekhara, Sudhakar <sudhakar.raj@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>