blkio: Export some symbols from blkio as its user CFQ can be a module

o blkio controller is inside the kernel and cfq makes use of interfaces
  exported by blkio. CFQ can be a module too, hence export symbols used
  by CFQ.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b00ca4c..7f3f343 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -961,7 +961,7 @@
 	unsigned int major, minor;
 
 	/* Do we need to take this reference */
-	if (!css_tryget(&blkcg->css))
+	if (!blkiocg_css_tryget(blkcg))
 		return NULL;;
 
 	cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
@@ -994,7 +994,7 @@
 	hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
 
 done:
-	css_put(&blkcg->css);
+	blkiocg_css_put(blkcg);
 	return cfqg;
 }