block: cgroups, kconfig, build bits for BFQ-v7r8-3.4

Update Kconfig.iosched and do the related Makefile changes to include
kernel configuration options for BFQ. Also add the bfqio controller
to the cgroups subsystem.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>

Change-Id: I1a25e7d742fbb92a9665795869417cec157481fa
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index 0bd390c..cbf22b1 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -72,3 +72,9 @@
 #endif
 
 /* */
+
+#ifdef CONFIG_CGROUP_BFQIO
+SUBSYS(bfqio)
+#endif
+
+/* */