ASoC: mt8192: revert "add audio afe document"

This reverts commit 1afc60e
(dt-bindings: mediatek: mt8192: add audio afe document).

 https://mailman.alsa-project.org/pipermail/alsa-devel/2020-November/176873.html
 These dependency are continuing to upstream, I will revert this patch first.
 After the dependencies are merged, I will send 'mt8192-afe-pcm.yaml' again.

[Massaged commit message to put hint about issue being fixed into there
rather than the trailer -- broonie]

Signed-off-by: Jiaxin Yu <jiaxin.yu@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1605081920-11848-1-git-send-email-jiaxin.yu@mediatek.com
Signed-off-by: Mark Brown <broonie@kernel.org>