ASoC: Samsung: Rename AC97 driver

Rename Samsung AC97 driver
	s3c-ac97.[c/h] -> ac97.[c/h]

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>