dm: rename device struct to udevice

using UBI and DM together leads in compiler error, as
both define a "struct device", so rename "struct device"
in include/dm/device.h to "struct udevice", as we use
linux code (MTD/UBI/UBIFS some USB code,...) and cannot
change the linux "struct device"

Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Marek Vasut <marex@denx.de>
diff --git a/include/dm/root.h b/include/dm/root.h
index 0ebccda..3018bc8 100644
--- a/include/dm/root.h
+++ b/include/dm/root.h
@@ -10,7 +10,7 @@
 #ifndef _DM_ROOT_H_
 #define _DM_ROOT_H_
 
-struct device;
+struct udevice;
 
 /**
  * dm_root() - Return pointer to the top of the driver tree
@@ -19,7 +19,7 @@
  *
  * @return pointer to root device, or NULL if not inited yet
  */
-struct device *dm_root(void);
+struct udevice *dm_root(void);
 
 /**
  * dm_scan_platdata() - Scan all platform data and bind drivers