clk: Fix build warnings

‘all_lists’ and ‘orphan_list’ is accessed only when DEBUG_FS is defined.
Thus, make their compilation conditional to fix the below warnings introduced
by commit 27b8d5f723 ("clk: flatten clk tree in debugfs"):
drivers/clk/clk.c:40:27: warning: ‘all_lists’ defined but not used [-Wunused-variable]
drivers/clk/clk.c:46:27: warning: ‘orphan_list’ defined but not used [-Wunused-variable]

Signed-off-by: Sachin Kamat <[e-mail]>
Cc: Peter De Schrijver <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

drivers/clk/clk.c

···
 static HLIST_HEAD(clk_orphan_list);
 static LIST_HEAD(clk_notifier_list);
 
-static struct hlist_head *all_lists[] = {
-	&clk_root_list,
-	&clk_orphan_list,
-	NULL,
-};
-
-static struct hlist_head *orphan_list[] = {
-	&clk_orphan_list,
-	NULL,
-};
-
 /***           locking             ***/
 static void clk_prepare_lock(void)
 {
···
 
 static struct dentry *rootdir;
 static int inited = 0;
+
+static struct hlist_head *all_lists[] = {
+	&clk_root_list,
+	&clk_orphan_list,
+	NULL,
+};
+
+static struct hlist_head *orphan_list[] = {
+	&clk_orphan_list,
+	NULL,
+};
 
 static void clk_summary_show_one(struct seq_file *s, struct clk *c, int level)
 {