ARM: S3C64XX: Make audio device code built unconditionally

Making the code depend on CONFIG_SND_S3C24XX_SOC means that if the ASoC
code is build modularily, the boards will fail to link due to the device
code also being built as a module.

As per Mark Brown's suggestions, just compile this always as it is expected
many machines will have audio.

Also move the obj-y line out of the device setup area into a new area just
for devices.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>