ASoC: audio-graph: respawn Platform Support

commit 63f2f9cc

 ("ASoC: audio-graph: remove Platform support")
removed Platform support from audio-graph, because it doesn't have
"plat" support on DT (simple-card has).
But, Platform support is needed if user is using
snd_dmaengine_pcm_register() which adds generic DMA as Platform.
And this Platform dev is using CPU dev.

Without this patch, at least STM32MP15 audio sound card is no more
functional (v5.13 or later). This patch respawn Platform Support on
audio-graph again.

Reported-by: Olivier MOYSAN <olivier.moysan@foss.st.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Olivier MOYSAN <olivier.moysan@foss.st.com>
Link: https://lore.kernel.org/r/878s0jzrpf.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>