ASoC: qdsp6: q6afe: use of_platform_populate/depopulate()

Now that the child nodes have there own compatible strings,
Use of_platform_populate/depopulate() instead of less common
of_platform_device_create()/destroy().

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Acked-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>