sunxi: Implement poweroff support for axp818 pmic

Adds poweroff support for axp818 pmic.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
index 02cb8e7..d137536 100644
--- a/drivers/power/Kconfig
+++ b/drivers/power/Kconfig
@@ -44,6 +44,7 @@
 config AXP818_POWER
 	boolean "axp818 pmic support"
 	depends on MACH_SUN8I_A83T
+	select CMD_POWEROFF
 	---help---
 	Say y here to enable support for the axp818 pmic found on
 	A83T dev board.