ASoC: mediatek: mt6359: Fix regulator_dev_lookup() fails for id "LDO_VAUD18"

ASoC: mediatek: mt6359: Fix regulator_dev_lookup() fails for id "LDO_VAUD18"

Mt6359 platform device is instantiated by mfd_add_devices(). In the
case, dev->of_node is NULL so that always fails to get the regulator_dev.

Use regualator-name "vaud18" that in dts node instead of
"LDO_VAUD19-supply". So that we can get regulator_dev through
regulator_lookup_by_name() directly.

Fixes: 41e35f234ab4 ("ASoC: Fix vaud18 power leakage of mt6359")
Signed-off-by: Jiaxin Yu <jiaxin.yu@mediatek.com>
Link: https://lore.kernel.org/r/1605841573-1442-2-git-send-email-jiaxin.yu@mediatek.com
Signed-off-by: Mark Brown <broonie@kernel.org>