ASoC: dmaengine_pcm: Allow passing component name via config

Merge series from Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>:

At the moment we cannot instantiate two dmaengine_pcms with the same
parent device, as the components will be named the same, leading to
conflicts.

Add 'name' field to the snd_dmaengine_pcm_config, and use that (if
defined) as the component name instead of deriving the component name
from the device.