tinyplay: add multichannel support

Improve the reading of the RIFF WAVE header so that unrecognised
chunks are skipped, which means that extra chunks are not played
as if they were audio data. This ensures that all channels for
multichannel playback line up correctly.

Change-Id: Ifdb3cb73b3c0bf41a1e271068d263cd01116616c
1 file changed