power: pmic: append rk818 regs to rk808

power: pmic: append rk818 regs to rk808

Both RK808 and RK818 chips are using a similar register map,
so we can reuse them.

I have also add reg prefix to exist registers, to keep them same style.

Signed-off-by: Jacob Chen <jacob-chen@iotwrt.com>
Reviewed-by: Simon Glass <sjg@chromium.org>