ASoC: msm: Reset pcm irq position in WRITE_DONE event

Pcm irq position is incremented by one extra period size if
WRITE_DONE event is received during paused state as elapsed
is not called and as a result playback gets muted sometimes
Fix this mute issue by resetting the pcm irq position in
WRITE_DONE event instead of pointer operation

Change-Id: Ia33e5188674b1f6a54619169b84bdd5be22ad73a
CRs-Fixed: 344436
Signed-off-by: Sriranjan Srikantam <cssrika@codeaurora.org>