dt-bindings: devfreq: event: convert Rockchip DFI binding to yaml

Convert the Rockchip DFI binding to yaml.

Link: https://lore.kernel.org/all/20231018061714.3553817-21-s.hauer@pengutronix.de/


Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Acked-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>