ARM: ep93xx: edb93xx: register audio platform device

Since the ASoC machine driver is now a platform driver we need to register a
matching platform device.

Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
Reviewed-by: Ryan Mallon <rmallon@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>