Add MTK SPM driver for suspend/resume scenario.

Signed-off-by: kenny liang <kenny.liang@mediatek.com>
Change-Id: I8207eea95914da9e63c62f3afc8329f3ccd9a22c

- Add PMIC driver
- Add RTC drvier
- Refactor PMIC and RTC to mediatek/common
- Implement system off handler

Change-Id: If76497646ace1b78bc9a5fa0110b652fe512281a
Signed-off-by: kenny liang <kenny.liang@mediatek.com>