msm: audio: qdsp6v2: Zero the cfg stack var

Write zeroes into the stack variable cfg to ensure
no previously written stack data is sent to
user-space.

Change-Id: Iea124d2528ed56d93e2a000027ff8bc30414d3fd
CRs-Fixed: 551574
Signed-off-by: Kenneth Westfield <kwestfie@codeaurora.org>
Merge "msm: audio: qdsp6v2: Zero the cfg stack var"