msm: qdsp6v2: memset stack buffer allocation.

This is needed to avoid garbage data in uninitialized variables.

Change-Id: I20e56ee32d3b9d1eecc4fa7761ff164a210fbbde
CRs-Fixed: 561611,561615
Signed-off-by: Mohammad Johny Shaik <mjshai@codeaurora.org>