OMAPDSS: fix return value check in create_dss_pdev()

In case of error, the function omap_device_alloc() returns ERR_PTR()
not NULL pointer. The NULL test in the return value check should
be replaced with IS_ERR().

dpatch engine is used to auto generated this patch.
(https://github.com/weiyj/dpatch)
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NTony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/display.c

@@ -221,7 +221,7 @@ static struct platform_device *create_dss_pdev(const char *pdev_name,
 
 	ohs[0] = oh;
 	od = omap_device_alloc(pdev, ohs, 1, NULL, 0);
-	if (!od) {
+	if (IS_ERR(od)) {
 		pr_err("Could not alloc omap_device for %s\n", pdev_name);
 		r = -ENOMEM;
 		goto err;