block: Fix double free in blk_integrity_unregister

Commit 3839e4b introduced a kobject_put but failed to remove the
kmem_cache_free beneath it, leading to a double free.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/blk-integrity.c b/block/blk-integrity.c
index 885cbb5..54bcba6 100644
--- a/block/blk-integrity.c
+++ b/block/blk-integrity.c
@@ -432,7 +432,6 @@
 	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);