ASoC: dt-bindings: asahi-kasei,ak5558: Fix the supply names

In the original txt format binding document ak4458.txt, the supply names
are 'AVDD-supply', 'DVDD-supply', and they are also used in driver. But in
the commit converting to yaml format, they are changed to 'avdd-supply',
'dvdd-supply'. After search all the dts file, these names 'AVDD-supply',
'DVDD-supply', 'avdd-supply', 'dvdd-supply' are not used in any dts
file. So it is safe to fix the yaml binding document.

Fixes: 829d78e3ea32 ("ASoC: dt-bindings: ak5558: Convert to dtschema")
Cc: stable@vger.kernel.org
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260212021829.3244736-4-shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>