ide: unregister idepnp driver on unload

idepnp driver is registered as a pnp driver on ide init but doesn't
get unregistered on ide unload causing driver list corruption and
eventually oops.  Fix it.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>

drivers/ide/ide-pnp.c

@@ -73,3 +73,8 @@ void __init pnpide_init(void)
 {
 	pnp_register_driver(&idepnp_driver);
 }
+
+void __exit pnpide_exit(void)
+{
+	pnp_unregister_driver(&idepnp_driver);
+}