dm: core: Rename sqq to seq_

Now that the sequence-numbering migration is complete, rename this member
back to seq_, adding an underscore to indicate it is internal to driver
model.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
diff --git a/test/dm/core.c b/test/dm/core.c
index cf66e27..b274b04 100644
--- a/test/dm/core.c
+++ b/test/dm/core.c
@@ -1075,10 +1075,10 @@
 
 	list_for_each_entry(uc, &gd->uclass_root, sibling_node) {
 		list_for_each_entry(dev, &uc->dev_head, uclass_node) {
-			if (dev->sqq == -1)
+			if (dev->seq_ == -1)
 				printf("Device '%s' has no seq (%d)\n",
-				       dev->name, dev->sqq);
-			ut_assert(dev->sqq != -1);
+				       dev->name, dev->seq_);
+			ut_assert(dev->seq_ != -1);
 		}
 	}