regulator: Add refactored mtk-dvfsrc-regulator driver

regulator: Add refactored mtk-dvfsrc-regulator driver

The previous driver never worked, and never got even compiled because
it was missing the DVFSRC driver entirely, including needed neaders.

This is a full (or nearly full) refactoring of the MediaTek DVFSRC
controlled Regulators driver, retaining support for the MT6873, MT8183
and MT8192 SoC, and adding MT8195.

As part of the refactoring, this driver is now probed using its own
devicetree compatible, as this is a child of the main DVFSRC driver
and gets probed as a subnode of that.

Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patch.msgid.link/20240610085735.147134-7-angelogioacchino.delregno@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>