asoc: msm: routing: add support for VA macro DMA interface

VA macro on Kona has three DMA TX ports. Add support routing
for the third VA macro DMA TX port to add backend and the
corresponding front ends.

Change-Id: I07298045292443af1220d9b95f4cd7aee0b79c66
Signed-off-by: Xiaoyu Ye <benyxy@codeaurora.org>