feat(mt8188): add reset and poweroff functions

- Add mtk_pm_system_reset_cros() for cros reset.
- Add mtk_pm_system_off_cros() for cros power-off.

TEST=build pass
BUG=b:236331724

Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Change-Id: I4117f6080e282551b37a936a490ab7b37ac31827