dm: Avoid accessing seq directly

At present various drivers etc. access the device's 'seq' member directly.
This makes it harder to change the meaning of that member. Change access
to go through a function instead.

The drivers/i2c/lpc32xx_i2c.c file is left unchanged for now.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/watchdog/tangier_wdt.c b/drivers/watchdog/tangier_wdt.c
index 358a9b9..bdc6559 100644
--- a/drivers/watchdog/tangier_wdt.c
+++ b/drivers/watchdog/tangier_wdt.c
@@ -80,7 +80,7 @@
 
 static int tangier_wdt_probe(struct udevice *dev)
 {
-	debug("%s: Probing wdt%u\n", __func__, dev->seq);
+	debug("%s: Probing wdt%u\n", __func__, dev_seq(dev));
 	return 0;
 }