c2port: fix device_create() return value check

Use IS_ERR() instead of comparing to NULL.

[akpm@linux-foundation.org: preserve the error code]
Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/c2port/core.c

@@ -912,8 +912,8 @@ struct c2port_device *c2port_device_register(char *name,
 
 	c2dev->dev = device_create(c2port_class, NULL, 0, c2dev,
 					"c2port%d", id);
-	if (unlikely(!c2dev->dev)) {
-		ret = -ENOMEM;
+	if (unlikely(IS_ERR(c2dev->dev))) {
+		ret = PTR_ERR(c2dev->dev);
 		goto error_device_create;
 	}
 	dev_set_drvdata(c2dev->dev, c2dev);