ARM: S3C64XX: Change dev-audio.c to use S3C_GPIO_SFN() for special functions

To aide in changing the gpio code, remove the use of pin-specific configs
and move to using the S3C_GPIO_SFN() versions.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>