ASoC: dt-bindings: mediatek: mt8192: re-add audio afe document

ASoC: dt-bindings: mediatek: mt8192: re-add audio afe document

The document was merged as commit 1afc60e00de3 ("dt-bindings:
mediatek: mt8192: add audio afe document").

However, [1] revealed that the commit 1afc60e00de3 breaks
dt_binding_check due to dt-bindings/clock/mt8192-clk.h doesn't
exist.

As a temporary fix, commit 7d94ca3c8acd ("ASoC: mt8192: revert
add audio afe document") reverted commit 1afc60e00de3.

dt-bindings/clock/mt8192-clk.h is in mainline per commit
f35f1a23e0e1 ("clk: mediatek: Add dt-bindings of MT8192 clocks").
Re-adds the document back.

[1]: https://mailman.alsa-project.org/pipermail/alsa-devel/2020-November/176873.html

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Message-Id: <20211008025523.1852319-1-tzungbi@google.com>
Signed-off-by: Mark Brown <broonie@kernel.org>