tsif: workaround for stuck dma

During tsif stress tests it was reported that the dma flush caused by
calling action_close() is sometimes unrecoverable.  The root cause is
stopping the tsif while a read by the dma of the tsif FIFO is in
progress.  This workaround works by starving the tsif FIFO allowing
any in-flight transfers to complete, and thus ensuring a clean shutdown.

CRs-Fixed: 357934
CRs-Fixed: 358384
Change-Id: I766f53abe4a6a6a5905caa55c2e7fa0afba5cff4
Signed-off-by: Joel Nider <jnider@codeaurora.org>