sunxi: axp221: Add support for controlling the drivebus pin

The axp221 / axp223's N_VBUSEN pin can be configured as an output rather
then an input, add axp_drivebus_enable() and _disable() functions to set
the pin in output mode and control it.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/include/axp221.h b/include/axp221.h
index e9552f6..e6639f1 100644
--- a/include/axp221.h
+++ b/include/axp221.h
@@ -45,11 +45,18 @@
 #define AXP221_ALDO1_CTRL	0x28
 #define AXP221_ALDO2_CTRL	0x29
 #define AXP221_ALDO3_CTRL	0x2a
+#define AXP221_VBUS_IPSOUT	0x30
+#define AXP221_VBUS_IPSOUT_DRIVEBUS	(1 << 2)
+#define AXP221_MISC_CTRL	0x8f
+#define AXP221_MISC_CTRL_N_VBUSEN_FUNC	(1 << 4)
 #define AXP221_PAGE		0xff
 
 /* Page 1 addresses */
 #define AXP221_SID		0x20
 
+/* We support drivebus control */
+#define AXP_DRIVEBUS
+
 int axp221_set_dcdc1(unsigned int mvolt);
 int axp221_set_dcdc2(unsigned int mvolt);
 int axp221_set_dcdc3(unsigned int mvolt);
@@ -64,3 +71,5 @@
 int axp221_set_aldo3(unsigned int mvolt);
 int axp221_init(void);
 int axp221_get_sid(unsigned int *sid);
+int axp_drivebus_enable(void);
+int axp_drivebus_disable(void);