net: libwx: fix an error code in wx_alloc_page_pool()

This function always returns success.  We need to preserve the error
code before setting rx_ring->page_pool = NULL.

Fixes: 850b971 ("net: libwx: Allocate Rx and Tx resources")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/Y+T4aoefc1XWvGYb@kili
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: error27

drivers/net/ethernet/wangxun/libwx/wx_lib.c

@@ -1745,8 +1745,8 @@ static int wx_alloc_page_pool(struct wx_ring *rx_ring)
 
 	rx_ring->page_pool = page_pool_create(&pp_params);
 	if (IS_ERR(rx_ring->page_pool)) {
-		rx_ring->page_pool = NULL;
 		ret = PTR_ERR(rx_ring->page_pool);
+		rx_ring->page_pool = NULL;
 	}
 
 	return ret;