msm: vidc: Increase CBR_VFR limit upto 720p@30fps

Currently CBR_VFR (CBR = constant bitrate, VFR = variable framerate
) is enabled upto 480p@30fps due to tighter bitrate convergence.
This change increases CBR_VBR limit upto 720p@30fps.

Change-Id: I452a28cbaabd3305ae61f41a0818f983e9dac516
Signed-off-by: Tapas Kumar Kundu <tkundu@codeaurora.org>