MediaTek Helio X10 MT6795 - MT6331/6332 Regulators

Merge series from AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>:

In an effort to give some love to the apparently forgotten MT6795 SoC,
I am upstreaming more components that are necessary to support platforms
powered by this one apart from a simple boot to serial console.

This series adds support for the regulators found in MT6331 and MT6332
main/companion PMICs.

Adding support to each driver in each subsystem is done in different
patch series as to avoid spamming uninteresting patches to maintainers.

Tested on a MT6795 Sony Xperia M5 (codename "Holly") smartphone.