techpack/codecs: AAC: Hardcode max_bitrate to 384k

Our DSP is supposed to support this.

Change-Id: Ib93ee2ec1b0c1a2fd1269f64d5f133db65d1b4a0
Suggested-by: Steve Kondik <shade@chemlab.org>
Signed-off-by: Panchajanya1999 <panchajanya@azure-dev.live>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>