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.c

@@ -1782,6 +1782,7 @@ done:
 }
 
 extern void pnpide_init(void);
+extern void pnpide_exit(void);
 extern void h8300_ide_init(void);
 
 /*
@@ -2094,6 +2095,10 @@ void cleanup_module (void)
 	for (index = 0; index < MAX_HWIFS; ++index)
 		ide_unregister(index);
 
+#ifdef CONFIG_BLK_DEV_IDEPNP
+	pnpide_exit();
+#endif
+
 #ifdef CONFIG_PROC_FS
 	proc_ide_destroy();
 #endif