hal_play_test: Fix for glitch in multichannel pcm playback

Amount of input data fed to MS12 in this usecase is very less,
which ends up in less amount of data at mixer_node. Hence increased
the amount of input data fed for pcm type.

Correcting parsing logic for play_list usecase.

Change-Id: I4e0e70ab7edfc8931df26a5e520a5dd35bfac5f3