ASoC: amd: memory release for rtd structure

rtd structure freed early may result in kernel panic in dma close
call back. moved releasing memory for rtd structure to the end of
dma close callback.

Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@amd.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>