RDMA/hns: Remove unnecessary ret variable from hns_roce_dereg_mr()

Fix the following coccicheck warning:

drivers/infiniband/hw/hns/hns_roce_mr.c:343:5-8: Unneeded variable: "ret".

Return 0 directly instead.

Link: https://lore.kernel.org/r/20220426070858.9098-1-guozhengkui@vivo.com


Signed-off-by: Guo Zhengkui <guozhengkui@vivo.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>