net: marvell: prestera: Fix return value check in prestera_kern_fib_cache_find()

rhashtable_lookup_fast() returns NULL pointer not ERR_PTR(), so
it can return fib_node directly in prestera_kern_fib_cache_find().
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220223084954.1771075-2-yangyingliang@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/prestera/prestera_router.c

@@ -68,7 +68,7 @@ prestera_kern_fib_cache_find(struct prestera_switch *sw,
 	fib_cache =
 	 rhashtable_lookup_fast(&sw->router->kern_fib_cache_ht, key,
 				__prestera_kern_fib_cache_ht_params);
-	return IS_ERR(fib_cache) ? NULL : fib_cache;
+	return fib_cache;
 }
 
 static void