ARM: S3C24XX: Add missing DMA device for Mini2440 board

Addition of s3c2440_device_dma was missed during conversion
from the Samsung legacy to the regular DMA API.
Add it so any devices using DMA, e.g I2S controller can
work properly.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>