x86: coreboot: Enable io command

Enable the io command for x86 on coreboot.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/coreboot.h b/include/configs/coreboot.h
index adeace0..d8aabd4 100644
--- a/include/configs/coreboot.h
+++ b/include/configs/coreboot.h
@@ -159,6 +159,7 @@
 #define CONFIG_CMD_GPIO
 #define CONFIG_CMD_IMI
 #undef CONFIG_CMD_IMLS
+#define CONFIG_CMD_IO
 #define CONFIG_CMD_IRQ
 #define CONFIG_CMD_ITEST
 #define CONFIG_CMD_LOADB