dt-bindings: regulator: mediatek,mt6332-regulator: Add missing compatible

dt-bindings: regulator: mediatek,mt6332-regulator: Add missing compatible

This binding had no compatible and for this reason would not be
applied to anything: add the missing "mediatek,mt6332-regulator"
compatible.

Fixes: e22943e32e1f regulator: ("Add bindings for MT6332 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>