RDMA/cma: Fix error flow in default_roce_mode_store

RDMA/cma: Fix error flow in default_roce_mode_store

[ Upstream commit 7c7b3e5d9aeed31d35c5dab0bf9c0fd4c8923206 ]

In default_roce_mode_store(), we took a reference to cma_dev, but didn't
return it with cma_dev_put in the error flow.

Fixes: 1c15b4f2a42f ("RDMA/core: Modify enum ib_gid_type and enum rdma_network_type")
Link: https://lore.kernel.org/r/20210113130214.562108-1-leon@kernel.org
Signed-off-by: Neta Ostrovsky <netao@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>