ASoC: DaVinci: pcm, don't play 1st sound period twice

Update the dma link with correct data as soon as
the master channel has copied it. Otherwise, the
1st period will play twice.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>