drm/sysfs: fix OOM verification

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

Reported-by: Juha Leppänen <[e-mail]>
Signed-off-by: David Herrmann <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/drm_sysfs.c

···
                 minor_str = "card%d";
 
 	minor->kdev = kzalloc(sizeof(*minor->kdev), GFP_KERNEL);
-	if (!minor->dev) {
+	if (!minor->kdev) {
 		r = -ENOMEM;
 		goto error;
 	}