ARM: EXYNOS: Add missing definition for IRQ_I2S0

This fixes following build error when sound support is selected
on EXYNOS4 platform.

sound/soc/samsung/idma.c: In function ‘idma_close’:
sound/soc/samsung/idma.c:327:11: error: ‘IRQ_I2S0’ undeclared (first use in this function)

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>