ASoC: samsung: Fix build on multiplatform

PCM and S/PDIF drivers referenced mach headers for a trivial
data structure. This caused build errors on multiplatform builds
as machine headers are not accessible from driver files. Move the data
structure definition to the driver header and remove the dependency.
While at it rename the structure to avoid multiple definition errors
as the same structure is also used by the platform code.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>