msm: qdsp5v2: Fix for noise issue during VOIP call

Driver discards the downlink packets when input queue is full.
Added code to block processing of downlink packets in the write()
till a input queue free slot is available for write.

(Taken from ICS Change-Id: I1198d9d9a98f27d3bd74a7e2fef647373e6d56cf)

Change-Id: Iffa54c378725147d0a9716e902d35ce9ce3f9dae
Signed-off-by: Shashi Kumar <sulege@codeaurora.org>