msm: qdsp6v2: memset stack buffer allocation.

This is needed to avoid garbage data in uninitialized variables.

Change-Id: Ic4b4d7481644c2add187a9122a4e7cfe7255b379
CRs-Fixed: 553304
Signed-off-by: Asish Bhattacharya <asishb@codeaurora.org>