mfd: rn5t618: Add Ricoh RN5T567 PMIC support

The Ricoh RN5T567 is from the same family as the Ricoh RN5T618 is,
the differences are:

+ DCDC4
+ Slightly different output voltage/currents
+ 32kHz Output
- ADC/Charger capabilities

Signed-off-by: Stefan Agner <stefan@agner.ch>
Reviewed-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>