RDMA/hns: fix memory leak in hns_roce_alloc_mr()

RDMA/hns: fix memory leak in hns_roce_alloc_mr()

[ Upstream commit a115aa00b18f7b8982b8f458149632caf64a862a ]

When hns_roce_mr_enable() failed in hns_roce_alloc_mr(), mr_key is not
released. Compiled test only.

Fixes: 9b2cf76c9f05 ("RDMA/hns: Optimize PBL buffer allocation process")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Link: https://lore.kernel.org/r/20221119070834.48502-1-shaozhengchao@huawei.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>