ASoC: SAMSUNG: Remove AC97 header file

This patch moves AC97 specific definitions, they doesn't need to be shared,
into 'ac97.c' from 'ac97.h'. This patch also remove header file, 'ac97.h',
and remove includes on machine drivers.

Signed-off-by: Seungwhan Youn <sw.youn@samsung.com>
Acked-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>