soc: mediatek: pwrap: add pwrap driver for MT6779 SoCs

MT6779 is a highly integrated SoCs, it uses PMIC_MT6359 for
power management. This patch adds pwrap master driver to
access PMIC_MT6359.

Signed-off-by: Argus Lin <argus.lin@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>