OMX Opus decoder omits sample rate / channel count

The OMX Opus decoder doesn't signal back the channel/samplerate info to
the framework, leading to a CTS failure when checking required values.

Based on an AOSP patch provided by denis.hsu@mediatek.com

Bug: 166695414
Test: CtsMediaTestCases android.media.cts.DecoderTest#testDecodeOpusChannelsAndRates
Change-Id: If710405caea4be6336b4aec3aa0c051ad3c0fe95