ASoC: do not close shared backend dailink

commit b1cd2e34c69a2f3988786af451b6e17967c293a0 upstream.

Multiple frontend dailinks may be connected to a backend
dailink at the same time. When one of frontend dailinks is
closed, the associated backend dailink should not be closed
if it is connected to other active frontend dailinks. Change
ensures that backend dailink is closed only after all
connected frontend dailinks are closed.

Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Patrick Lai <plai@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>