tinyplay: Fix pop issue at the end of playback.

Pop issue is observed at the end of playback for certain contents.
Wave file format data description header contains actual size
of sound data included in the data section. Use this data size
information for processing actual raw bytes, which avoids reading
extra bytes and avoids pop issue.

Change-Id: I71b881ec7d7b5e1fc688d54061751e6f4527bcc5
CRs-fixed: 613569