OpenSL ES: volume support for QAudioInput.

The OpenSL volume interface is not available for audio inputs on
Android so we apply the volume ourselves on the PCM data.

Task-number: QTBUG-42159
Change-Id: If43d8aa576bc70a925681f0db1ca8b40e71f7b29
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>