ASoC: msm: qdspv2: Fix junk characters in session name

Initialize MVM session name array to zero to avoid junk
characters at the end.

Change-Id: Ie14c56fee8c795f8ebd68124b187c2c8ebae3a06
CRs-fixed: 702741
Signed-off-by: Karthik Reddy Katta <a_katta@codeaurora.org>