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: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Tony Lindgren <tony@atomide.com>
diff --git a/arch/arm/mach-omap2/display.c b/arch/arm/mach-omap2/display.c
index 7012068..a51ece4 100644
--- a/arch/arm/mach-omap2/display.c
+++ b/arch/arm/mach-omap2/display.c
@@ -221,7 +221,7 @@
 
 	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;