ASoC: qdsp6v2: Flush record session during stop

It is recommended for record session to be flushed during
stop to ensure that there is no problem after resuming the
session.

Change-Id: I0bfc22f335e141630d473fc0dd9437a0b47e0785
Signed-off-by: Chaithanya Krishna Bacharaju <chaithan@codeaurora.org>