ASoC: msm: Add 8-channel Multi-PCM TX support

There is use case that the HDMI input goes through MI2S TX
interface to ADSP. Add 8-channel Multi-PCM TX support for this
use case.

Change-Id: Ie26e188da8d15988452103f11277944551344cd1
Signed-off-by: Subhash Chandra Bose Naripeddy <snariped@codeaurora.org>