mfd: rk808: Add RK817 and RK809 support

The RK809 and RK817 are a Power Management IC (PMIC) for multimedia
and handheld devices. They contains the following components:
  - Regulators
  - RTC
  - Clocking

Both RK809 and RK817 chips are using a similar register map,
so we can reuse the RTC and Clocking functionality.
Most of regulators have a some implementation also.

Signed-off-by: Tony Xie <tony.xie@rock-chips.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>