ARM: S3C6410: Declare IISv4 audio-bus clock

Declare 'audio-bus' clock for IISv4 controller of S3C6410.
Even though the name is same as that for IISv3, the id is
set to -1(just one instance of the controller is available)
which helps always fetch the correct clock.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>