dt-bindings: mediatek: mt6359: Add new property for mt6359

This patch add "LDO_VAUD18-supply" property to
control vaud18 regulator. It is labeled as required
due to mt6359 audio path always need to enable vaud18.

Signed-off-by: Shane.Chien <shane.chien@mediatek.com>
Link: https://lore.kernel.org/r/1604975492-6142-3-git-send-email-shane.chien@mediatek.com


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