!761 net: stmmac: fix potential double free of dma descriptor resources

Merge Pull Request from: @Hongchen_Zhang 
 
a double free problem in stmmac driver was triggered when doing mugen test,
After apply this patch the double free problem disappear. 
 
Link:https://gitee.com/openeuler/kernel/pulls/761

 

Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com>
Reviewed-by: Guo Dongtai <guodongtai@kylinos.cn>
Reviewed-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>