ARM: hisi: handle of_iomap and fix missing of_node_put

Relying on an unchecked of_iomap() which can return NULL is problematic
here, an explicit check seems mandatory. Also the call to
of_find_compatible_node() returns a device node with refcount incremented
therefor an explicit of_node_put() is needed here.
Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Fixes: commit 22bae429 ("ARM: hi3xxx: add hotplug support")
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>

arch/arm/mach-hisi/hotplug.c

@@ -148,13 +148,20 @@ static int hi3xxx_hotplug_init(void)
 	struct device_node *node;
 
 	node = of_find_compatible_node(NULL, NULL, "hisilicon,sysctrl");
-	if (node) {
-		ctrl_base = of_iomap(node, 0);
-		id = HI3620_CTRL;
-		return 0;
+	if (!node) {
+		id = ERROR_CTRL;
+		return -ENOENT;
 	}
-	id = ERROR_CTRL;
-	return -ENOENT;
+
+	ctrl_base = of_iomap(node, 0);
+	of_node_put(node);
+	if (!ctrl_base) {
+		id = ERROR_CTRL;
+		return -ENOMEM;
+	}
+
+	id = HI3620_CTRL;
+	return 0;
 }
 
 void hi3xxx_set_cpu(int cpu, bool enable)