ASoC: documentation updates

This patch is only for RFC purpose of ASoC documentation updates which
match with current ASoC codes with documents. Mostly modify features
are modified to be sync with changes after multi-component patches.

Signed-off-by: Seungwhan Youn <sw.youn@samsung.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>