ASoC: q6asm: add length to write command token

Add length to write command packet token so that we can track exactly
how many bytes are consumed by DSP in the command reply.

This is useful in some use-cases where the end of the file/stream
is not aligned with period size.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Tested-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20200727093806.17089-5-srinivas.kandagatla@linaro.org


Signed-off-by: Mark Brown <broonie@kernel.org>