ASoC: msm: qdsp6v2: Use EOS status flag for TRIGGER DRAIN

Update TRIGGER DRAIN function to use the EOS specific status
flag while waiting for ACK of EOS command.

Change-Id: I77bdad3e61ede3651c712d2d0d8b8a487b1a0a11
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>