video: msm: Increase video encoding output buffer size

When bistream buffer size is half of YUV buffer size, video core
may be put into a bad state where output buffers are not returned
back to user space. Increasing the output buffer size solves the issue.

Change-Id: Ie30ec084a764717526c74fc3f89d2684c7020f09
Signed-off-by: Shuzhen Wang <shuzhenw@codeaurora.org>