dm: Rename U_BOOT_DRIVER_ALIAS to DM_DRIVER_ALIAS

We use the U_BOOT_ prefix (i.e. U_BOOT_DRIVER) to declare a driver but
in every other case we just use DM_. Update the alias macros to use the
DM_ prefix.

We could perhaps rename U_BOOT_DRIVER() to DM_DRIVER(), but this macro
is widely used and there is at least some benefit to indicating it us a
U-Boot driver, particularly for code ported from Linux. So for now, let's
keep that name.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/dm/device.h

@@ -343,7 +343,7 @@ struct driver {
  * produce no code but its information will be parsed by tools like
  * dtoc
  */
-#define U_BOOT_DRIVER_ALIAS(__name, __alias)
+#define DM_DRIVER_ALIAS(__name, __alias)
 
 /**
  * dev_get_plat() - Get the platform data for a device