drm/omap: Use ERR_CAST directly instead of ERR_PTR(PTR_ERR())

We prefer to use ERR_CAST to do so.
The issue is detected with the help of Coccinelle.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/dss.c

@@ -947,7 +947,7 @@ dss_debugfs_create_file(struct dss_device *dss, const char *name,
 				&dss_debug_fops);
 	if (IS_ERR(d)) {
 		kfree(entry);
-		return ERR_PTR(PTR_ERR(d));
+		return ERR_CAST(d);
 	}
 
 	entry->dentry = d;