dm: Switch over to use new sequence number for dev_seq()

Update this function to use the new sequence number and fix up the test
that deals with this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index f3b7662..fb83804 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -33,7 +33,7 @@
 		testfdt6 = "/e-test";
 		testbus3 = "/some-bus";
 		testfdt0 = "/some-bus/c-test@0";
-		testfdt1 = "/some-bus/c-test@1";
+		testfdt12 = "/some-bus/c-test@1";
 		testfdt3 = "/b-test";
 		testfdt5 = "/some-bus/c-test@5";
 		testfdt8 = "/a-test";