drm/ttm: fix refcounting in ttm global code.

the global refcount wasn't being increased after the first reference.
this caused an oops on unload on a multi-gpu card.

Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/ttm/ttm_global.c

@@ -82,8 +82,8 @@ int ttm_global_item_ref(struct ttm_global_reference *ref)
 		if (unlikely(ret != 0))
 			goto out_err;
 
-		++item->refcount;
 	}
+	++item->refcount;
 	ref->object = item->object;
 	object = item->object;
 	mutex_unlock(&item->mutex);