ARM: S3C64XX: Clear DMA_HALT upon start

The stop function sets the DMA_HALT bit, which prevents
the DMA transfer to resume after stop, for example during
audio PAUSE/PLAY cycle. Clear the HALT bit during start.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>