voice_svc : Fix crash in voice_svc driver during SSR

Current implementation allocates invalid amount of
memory for payload when RESET_EVENTS is received.
Set the payload size to zero. Avoid allocating
and accessing the payload memory for RESET_EVENTS.

CRs-fixed: 798906
Change-Id: I5c07785d516d2f64d9bd183d3b91b8cf069f43d5
Signed-off-by: Karthik Reddy Katta <a_katta@codeaurora.org>