Fix Opus encoder being set to CBR

The code is currently setting unconstrained CBR, instead of constrained
VBR. The OPUS_SET_VBR argument should be 1, or not set at all, to
be VBR. (libopus docs for OPUS_SET_VBR: https://mf4.xiph.org/jenkins/view/opus/job/opus/ws/doc/html/group__opus__encoderctls.html#ga34d09ae06cab7e1a6c49876249b67892)

Bug: 131410994
Test: Verify AGSA Opus encoder receives varying Opus frame sizes.
Change-Id: Ife8340f720a0faedd748c61d6a69bb30dfe30706
1 file changed