soc: mediatek: pm-domains: Add buck isolation setting in power domain

In some chipsets, we need to disable EXT_BUCK_ISO before turning on the
specific power pm-domains (mtcmos), such as ADSP in MT8192 and CAM_VCORE
in MT8188.

Add the MTK_SCPD_EXT_BUCK_ISO flag to control the buck isolation setting
in the mediatek power domain driver.

Signed-off-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20230117032640.13504-3-allen-kh.cheng@mediatek.com
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>