ASoC: SAMSUNG: Add Kconfig to support SMDK4212

This patch adds Kconfig to support SMDK4212.
SMDK4212 is based on samsung exynos4212 SoC.
And WM8994 is used for audio codec.

Signed-off-by: Sangbeom Kim <sbkim73@samsung.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>