ASoC: msm: qdsp6v2: Clear HDMI channel allocation on shutdown

On shutdown of the HDMI Q6 driver clear the channel
allocation structure. If the channel allocation is
not properly cleared the next session to use the
driver may inncorrectly use the channel allocation
from the previous configuration.

Change-Id: Id033958031dc509c6b3060d892bccf5b1c60524b
Signed-off-by: Ben Romberger <bromberg@codeaurora.org>