ASoC: dt-bindings: rockchip: Convert pdm bindings to yaml

This patch converts pdm bindings to yaml.

Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1630675438-3418-2-git-send-email-sugar.zhang@rock-chips.com


Signed-off-by: Mark Brown <broonie@kernel.org>