bootstage: Record the time taken to set up driver model

Driver model is set up ones before relocation and once after. Record the
time taken in each case.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/board_r.c b/common/board_r.c
index bde9877..ef90998 100644
--- a/common/board_r.c
+++ b/common/board_r.c
@@ -313,7 +313,9 @@
 #ifdef CONFIG_TIMER
 	gd->timer = NULL;
 #endif
+	bootstage_start(BOOTSTATE_ID_ACCUM_DM_R, "dm_r");
 	ret = dm_init_and_scan(false);
+	bootstage_accum(BOOTSTATE_ID_ACCUM_DM_R);
 	if (ret)
 		return ret;
 #ifdef CONFIG_TIMER_EARLY