pch_dma: fix dma direction issue for ML7213 IOH video-in

Currently, even-channel number is set as tx direction and odd is set as rx.
However, though video-in uses ch6, the direction is not tx but rx.
This patch sets video-in's DMA direction correctly.

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>