event: Convert arch_cpu_init_dm() to use events

Instead of a special function, send an event after driver model is inited
and adjust the boards which use this function.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/core/root.c

@@ -404,6 +404,11 @@ int dm_init_and_scan(bool pre_reloc_only)
 			return ret;
 		}
 	}
+	if (CONFIG_IS_ENABLED(DM_EVENT)) {
+		ret = event_notify_null(EVT_DM_POST_INIT);
+		if (ret)
+			return log_msg_ret("ev", ret);
+	}
 
 	return 0;
 }