sunxi: Implement poweroff support for axp221 pmic

Adds poweroff support for axp221 pmic.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index 52c9e61..dfd60aa 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -36,6 +36,7 @@
 config AXP221_POWER
 	boolean "axp221 / axp223 pmic support"
 	depends on MACH_SUN6I || MACH_SUN8I_A23 || MACH_SUN8I_A33
+	select CMD_POWEROFF
 	---help---
 	Select this to enable support for the axp221/axp223 pmic found on most
 	A23 and A31 boards.