mfd: rn5t618: Document device tree bindings
mfd: rn5t618: Document device tree bindings

This adds the device tree bindings documentation for Ricoh RN5T618.

Signed-off-by: Beniamino Galvani <0a204c0ed8670f52f51e6619404e025b8f375a15@gmail.com>
Reviewed-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@linaro.org>
Signed-off-by: Lee Jones <630e34333487a351a857f6b705e04d30b37c1629@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs