power: pmic: rk817: support rk817 pmic

The RK817 is a Power Management IC (PMIC) for multimedia
and handheld devices. They contains the following components:
    - Regulators(4*BUCKs, 1* BOOST, 9*LDOs, 1*SWITCH)
    - 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>