ARM: OMAP2+: Fix an IS_ERR() vs NULL check in _get_pwrdm()

The of_clk_get() function returns error pointers, it never returns NULL.

Fixes: 4ea3711 ("ARM: OMAP2+: omap-iommu.c conversion to ti-sysc")
Signed-off-by: Jing Xiangfeng <jingxiangfeng@huawei.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Author: hiss2018

arch/arm/mach-omap2/omap-iommu.c

@@ -74,7 +74,7 @@ static struct powerdomain *_get_pwrdm(struct device *dev)
 		return pwrdm;
 
 	clk = of_clk_get(dev->of_node->parent, 0);
-	if (!clk) {
+	if (IS_ERR(clk)) {
 		dev_err(dev, "no fck found\n");
 		return NULL;
 	}