staging: dgnc: add __exit macro to dgnc_driver.c

Add the __exit macro to the dgnc_cleanup_module(void) function
in dgnc_driver.c
Signed-off-by: Joshua Houghton <josh@awful.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/dgnc/dgnc_driver.c

@@ -158,7 +158,7 @@ static void cleanup(bool sysfiles)
  *
  * Module unload.  This is where it all ends.
  */
-static void dgnc_cleanup_module(void)
+static void __exit dgnc_cleanup_module(void)
 {
 	cleanup(true);
 	pci_unregister_driver(&dgnc_driver);