Previously, the ASoC 'platform' (PCM/DMA) object was instantiated via a
platform_device. This didn't represent the hardware well, since there
was no separate hardware associated with this platform_device; it was a
virtual device with sole purpose to call snd_soc_register_platform().
This mechanism required all board files to register this device, and all
ASoC machine drivers to create and register this device when booting
using device tree.

This change removes the platform_device completely. Each Tegra DAI now
registers the ASoC 'platform' itself. Machine drivers are adjusted for
the new 'platform' name.
Signed-off-by: NStephen Warren <swarren@wwwdotorg.org>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>