cmd_boot: Add a poweroff command

Add a 'poweroff' command to boot commands, this only gets enabled if the
board Kconfig does a "select CMD_POWEROFF".

Signed-off-by: Michael van Slingerland <michael@deviousops.nl>
[hdegoede@redhat.com: Make the cmd conditional on a CMD_POWEROFF Kconfig]
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/common/cmd_boot.c b/common/cmd_boot.c
index 8f2e070..72f2cf3 100644
--- a/common/cmd_boot.c
+++ b/common/cmd_boot.c
@@ -61,3 +61,11 @@
 	"Perform RESET of the CPU",
 	""
 );
+
+#ifdef CONFIG_CMD_POWEROFF
+U_BOOT_CMD(
+	poweroff, 1, 0,	do_poweroff,
+	"Perform POWEROFF of the device",
+	""
+);
+#endif