Add new bootstage step for the main loop

Mark when we get to the main loop.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/main.c b/common/main.c
index 5362781..b145f85 100644
--- a/common/main.c
+++ b/common/main.c
@@ -376,6 +376,8 @@
 	char bcs_set[16];
 #endif /* CONFIG_BOOTCOUNT_LIMIT */
 
+	bootstage_mark_name(BOOTSTAGE_ID_MAIN_LOOP, "main_loop");
+
 #ifdef CONFIG_BOOTCOUNT_LIMIT
 	bootcount = bootcount_load();
 	bootcount++;