block: Fix double free in blk_integrity_unregister

Commit 3839e4b2 introduced a kobject_put but failed to remove the
kmem_cache_free beneath it, leading to a double free.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NJens Axboe <jaxboe@fusionio.com>

block/blk-integrity.c

@@ -432,7 +432,6 @@ void blk_integrity_unregister(struct gendisk *disk)
 	kobject_uevent(&bi->kobj, KOBJ_REMOVE);
 	kobject_del(&bi->kobj);
 	kobject_put(&bi->kobj);
-	kmem_cache_free(integrity_cachep, bi);
 	disk->integrity = NULL;
 }
 EXPORT_SYMBOL(blk_integrity_unregister);