soc: mediatek: pwrap: fix fatal compiler error

When adding the MT6380 compatible, the sentinel for of_device_id was
deleted, which leades to the following compiler error:
FATAL: drivers/soc/mediatek/mtk-pmic-wrap: struct of_device_id is not terminated with a NULL entry!

Fix this by adding the sentinel again.

Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>