Add optional CONFIG_BLK_CGROUP and CONFIG_IOSCHED_CFQ to check-config.sh

It is needed for blkio.weight support

Signed-off-by: Alexander Morozov <lk4d4@docker.com>

contrib/check-config.sh

@@ -184,6 +184,8 @@ echo 'Optional Features:'
 }
 flags=(
 	RESOURCE_COUNTERS
+	BLK_CGROUP
+	IOSCHED_CFQ
 	CGROUP_PERF
 	CFS_BANDWIDTH
 )