ASoC: soc-utils: respawn dummy Platform

commit 64ee5067 ("ASoC: soc-utils: remove dummy Platform") removed
dummy Platform from ALSA SoC, but it is over-kill.
This patch respawn it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>