ASoC: add phycore-ac97 sound support

This patch adds sound support for Phytec PhyCORE / PhyCARD
modules in AC97 mode.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>