mfd: rn5t618: Add a power supply subdevice

The RN5T618 and RC5T619 both have a charger and a fuel gauge, so add
a subdevice for it. According to drivers in the wild, things
should be at least similar, but since it is not tested, add it
only to the RC5T619.
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/rn5t618.c

@@ -25,6 +25,7 @@ static const struct mfd_cell rn5t618_cells[] = {
 
 static const struct mfd_cell rc5t619_cells[] = {
 	{ .name = "rn5t618-adc" },
+	{ .name = "rn5t618-power" },
 	{ .name = "rn5t618-regulator" },
 	{ .name = "rc5t619-rtc" },
 	{ .name = "rn5t618-wdt" },