drm/sysfs: fix OOM verification

Copy/Paste typo.. we need to test for ->kdev instead of ->dev.

Reported-by: Juha Leppänen <juha_efku@dnainternet.net>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_sysfs.c

@@ -516,7 +516,7 @@ int drm_sysfs_device_add(struct drm_minor *minor)
                 minor_str = "card%d";
 
 	minor->kdev = kzalloc(sizeof(*minor->kdev), GFP_KERNEL);
-	if (!minor->dev) {
+	if (!minor->kdev) {
 		r = -ENOMEM;
 		goto error;
 	}