Correct SPL use of CMD_BCB

This converts 1 usage of this option to the non-SPL form, since there is
no SPL_CMD_BCB defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/bcb.h b/include/bcb.h
index 897e83d..5edb17a 100644
--- a/include/bcb.h
+++ b/include/bcb.h
@@ -8,7 +8,7 @@
 #ifndef __BCB_H__
 #define __BCB_H__
 
-#if CONFIG_IS_ENABLED(CMD_BCB)
+#if IS_ENABLED(CONFIG_CMD_BCB)
 int bcb_write_reboot_reason(int devnum, char *partp, const char *reasonp);
 #else
 #include <linux/errno.h>