dt-bindings: mfd: Add compatible for the MediaTek MT6366 PMIC

This adds compatible for the MediaTek MT6366 PMIC.

Signed-off-by: Johnson Wang <johnson.wang@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20220106065407.16036-4-johnson.wang@mediatek.com