video: ipu: Fix dereferencing NULL pointer problem

The clk_set_rate function dereferences the clk pointer without
checking whether it is NULL. This may cause problem when clk is NULL.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>

drivers/video/ipu_common.c

@@ -132,8 +132,12 @@ struct clk *clk_get_parent(struct clk *clk)
 
 int clk_set_rate(struct clk *clk, unsigned long rate)
 {
-	if (clk && clk->set_rate)
+	if (!clk)
+		return 0;
+
+	if (clk->set_rate)
 		clk->set_rate(clk, rate);
+
 	return clk->rate;
 }