ASoC: q6dsp: q6afe: add global q6afe waitqueue

In some cases like clocks q6afe would have to process commands
without an associated q6afe port, in such cases waitqueue is
required at global level to wait for the command to finish.
This patch also adds the command result to go with this waitqueue.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>