ASoC: codecs: Remove the "fade-enable property"

Remove the "fade-enable" property because the "fade_step" property
already implement this functionality.

Signed-off-by: Weidong Wang <wangweidong.a@awinic.com>
Link: https://lore.kernel.org/r/20230928105727.47273-4-wangweidong.a@awinic.com


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