dt-bindings: regulator: mediatek,mt6331: Fix various regulator names

dt-bindings: regulator: mediatek,mt6331: Fix various regulator names

This binding was never applied to anything because it misses the
compatible, hence any mistake in it got unnoticed.

Before adding the compatible to let it apply, fix the names and
the node names of various regulators.

Fixes: 6385e21692bb ("regulator: Add bindings for MT6331 regulator")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>