power: pmic: rk809: support rk809 pmic

The RK809 is a Power Management IC (PMIC) for multimedia
and handheld devices. They contains the following components:
    - Regulators(5*BUCKs, 9*LDOs, 2*SWITCHes)
    - RTC
    - Clocking

Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>