block: remove ioc_*_changed()

After the previous patch to cfq, there's no ioc_get_changed() user
left.  This patch yanks out ioc_{ioprio|cgroup|get}_changed() and all
related stuff.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/ioprio.c b/fs/ioprio.c
index 0f1b951..4864437 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -50,7 +50,7 @@
 
 	ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
 	if (ioc) {
-		ioc_ioprio_changed(ioc, ioprio);
+		ioc->ioprio = ioprio;
 		put_io_context(ioc);
 	}