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/include/dm/device.h b/include/dm/device.h
index ed80ae44..7ada720 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -182,6 +182,11 @@
 	return ofnode_valid(dev->node);
 }
 
+static inline int dev_seq(const struct udevice *dev)
+{
+	return dev->seq;
+}
+
 /**
  * struct udevice_id - Lists the compatible strings supported by a driver
  * @compatible: Compatible string