cfq-iosched: move group scheduling functions under ifdef

If CFQ_GROUP_IOSCHED is not set, the compiler produces the
following warning:

  CC      block/cfq-iosched.o
  linux/block/cfq-iosched.c:469:2:
    warning: 'cpd_to_cfqgd' defined but not used [-Wunused-function]
    *cpd_to_cfqgd(struct blkcg_policy_data *cpd)
     ^

In reality, two other lookup functions aren't used either if
CFQ_GROUP_IOSCHED isn't set. Move all three under one of the
CFQ_GROUP_IOSCHED sections in the code.
Reported-by: NVladimir Zapolskiy <vz@mleia.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

block/cfq-iosched.c

@@ -460,22 +460,6 @@ CFQ_CFQQ_FNS(deep);
 CFQ_CFQQ_FNS(wait_busy);
 #undef CFQ_CFQQ_FNS
 
-static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
-{
-	return pd ? container_of(pd, struct cfq_group, pd) : NULL;
-}
-
-static struct cfq_group_data
-*cpd_to_cfqgd(struct blkcg_policy_data *cpd)
-{
-	return cpd ? container_of(cpd, struct cfq_group_data, pd) : NULL;
-}
-
-static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
-{
-	return pd_to_blkg(&cfqg->pd);
-}
-
 #if defined(CONFIG_CFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
 
 /* cfqg stats flags */
@@ -620,6 +604,22 @@ static inline void cfqg_stats_update_avg_queue_size(struct cfq_group *cfqg) { }
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
 
+static inline struct cfq_group *pd_to_cfqg(struct blkg_policy_data *pd)
+{
+	return pd ? container_of(pd, struct cfq_group, pd) : NULL;
+}
+
+static struct cfq_group_data
+*cpd_to_cfqgd(struct blkcg_policy_data *cpd)
+{
+	return cpd ? container_of(cpd, struct cfq_group_data, pd) : NULL;
+}
+
+static inline struct blkcg_gq *cfqg_to_blkg(struct cfq_group *cfqg)
+{
+	return pd_to_blkg(&cfqg->pd);
+}
+
 static struct blkcg_policy blkcg_policy_cfq;
 
 static inline struct cfq_group *blkg_to_cfqg(struct blkcg_gq *blkg)