drm/nouveau: do not leak in nv20_graph_create

If we return due to an unknown chipset in
drivers/gpu/drm/nouveau/nv20_graph.c:nv20_graph_create() we'll leak the
memory allocated to 'pgraph'.

This patch should fix the leak.

Signed-off-by: Jesper Juhl <[e-mail]>
Reviewed-by: Marcin Slusarz <[e-mail]>
Signed-off-by: Ben Skeggs <[e-mail]>

drivers/gpu/drm/nouveau/nv20_graph.c

···
 			break;
 		default:
 			NV_ERROR(dev, "PGRAPH: unknown chipset\n");
+			kfree(pgraph);
 			return 0;
 		}
 	} else {
···
 			break;
 		default:
 			NV_ERROR(dev, "PGRAPH: unknown chipset\n");
+			kfree(pgraph);
 			return 0;
 		}
 	}