msm: qdsp6v2: memset stack buffer allocation.

This is needed to avoid garbage data in uninitialized variables.

Change-Id: Ia8e6148eef2cafe6931c6fdc35d7aafeb0c0bd97
CRs-Fixed: 556792
Signed-off-by: Asish Bhattacharya <asishb@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>