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/test/dm/test-main.c b/test/dm/test-main.c
index 828ed46..fbdae68 100644
--- a/test/dm/test-main.c
+++ b/test/dm/test-main.c
@@ -32,7 +32,7 @@
 /* Ensure all the test devices are probed */
 static int do_autoprobe(struct dm_test_state *dms)
 {
-	struct device *dev;
+	struct udevice *dev;
 	int ret;
 
 	/* Scanning the uclass is enough to probe all the devices */