msm: vidc: add additional check to avoid out of bound access

pkt->msg_size can be corrupted and that leads to OOB access. So added
additional conditional check to avoid OOB access in debug queue
packet handling.

Change-Id: I360812c40369ecef2dd99464d400661bc785074b
Signed-off-by: Govindaraj Rajagopal <grajagop@codeaurora.org>
Signed-off-by: Sanjay Singh <sisanj@codeaurora.org>