mfd: axp20x: Add support for RSB based AXP223 PMIC

The AXP223 is a new PMIC commonly paired with Allwinner A23/A33 SoCs.
It is functionally identical to AXP221; only the regulator default
voltage/status and the external host interface are different.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index dba4f99..c69ea74 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -112,6 +112,7 @@
 obj-$(CONFIG_MFD_DA9052_I2C)	+= da9052-i2c.o
 obj-$(CONFIG_MFD_AXP20X)	+= axp20x.o
 obj-$(CONFIG_MFD_AXP20X_I2C)	+= axp20x-i2c.o
+obj-$(CONFIG_MFD_AXP20X_RSB)	+= axp20x-rsb.o
 
 obj-$(CONFIG_MFD_LP3943)	+= lp3943.o
 obj-$(CONFIG_MFD_LP8788)	+= lp8788.o lp8788-irq.o