mm-video: vdec: increase o/p buffer count in testapp

For anti-flicker mode, the test app holds on to one o/p
buffer always. Without this change, for some clips we
see a freeze happening as venus expects all output buffers
to be queued, but the test app holds on to one output
buffer.

CRs-fixed: 485149
Change-Id: I4fdc09dc6d812e5c8524d19054904a28ac380051
1 file changed