mfd: axp20x: Add support for AXP813 PMIC

The X-Powers AXP813 PMIC is normally used with Allwinner's A83T SoC.
It has the same range of functions as other X-Powers PMICs, such as
DC-DC buck converter and linear regulator outputs, AC-IN and VBUS
power supplies, power button trigger, GPIOs, ADCs, and a battery
charger.

Note that the IRQ table given in the datasheet is incorrect: in IRQ
enable/status registers 1, there are separate IRQs for ACIN and VBUS,
instead of bits [7:5] being the same as bits [4:2]. So it shares the
same IRQs as the AXP803, rather than the AXP288.

This patch adds basic mfd support for it, with only the power button
enabled.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

include/linux/mfd/axp20x.h

@@ -23,6 +23,7 @@ enum axp20x_variants {
 	AXP803_ID,
 	AXP806_ID,
 	AXP809_ID,
+	AXP813_ID,
 	NR_AXP20X_VARIANTS,
 };
 
@@ -387,6 +388,34 @@ enum {
 	AXP803_REG_ID_MAX,
 };
 
+enum {
+	AXP813_DCDC1 = 0,
+	AXP813_DCDC2,
+	AXP813_DCDC3,
+	AXP813_DCDC4,
+	AXP813_DCDC5,
+	AXP813_DCDC6,
+	AXP813_DCDC7,
+	AXP813_ALDO1,
+	AXP813_ALDO2,
+	AXP813_ALDO3,
+	AXP813_DLDO1,
+	AXP813_DLDO2,
+	AXP813_DLDO3,
+	AXP813_DLDO4,
+	AXP813_ELDO1,
+	AXP813_ELDO2,
+	AXP813_ELDO3,
+	AXP813_FLDO1,
+	AXP813_FLDO2,
+	AXP813_FLDO3,
+	AXP813_RTC_LDO,
+	AXP813_LDO_IO0,
+	AXP813_LDO_IO1,
+	AXP813_SW,
+	AXP813_REG_ID_MAX,
+};
+
 /* IRQs */
 enum {
 	AXP152_IRQ_LDO0IN_CONNECT = 1,