sunxi: axp221: Protect axp221_init against multiple calls

The voltage setting code knows it needs to call axp221_init before calling
the various voltage setting functions.

But users of axp utility functions like axp221_get_sid() do not know this,
so the utility functions always call axp221_init() to ensure that the
p2wi / rsb setup magic has been done.

Since doing this repeatedly is quite expensive, add a check to axp221_init
so that it only does the initialization once.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>

drivers/power/axp221.c

@@ -304,9 +304,14 @@ int axp221_set_aldo3(unsigned int mvolt)
 
 int axp221_init(void)
 {
+	/* This cannot be 0 because it is used in SPL before BSS is ready */
+	static int needs_init = 1;
 	u8 axp_chip_id;
 	int ret;
 
+	if (!needs_init)
+		return 0;
+
 	ret = pmic_bus_init();
 	if (ret)
 		return ret;
@@ -318,6 +323,7 @@ int axp221_init(void)
 	if (!(axp_chip_id == 0x6 || axp_chip_id == 0x7 || axp_chip_id == 0x17))
 		return -ENODEV;
 
+	needs_init = 0;
 	return 0;
 }