RDMA/cm: Fix access to uninitialized variable

The ndev will be initialized and held only for successful
ib_get_cached_gid(), otherwise it is garbage stack memory.
Calling dev_put() in failure path is wrong.

Fixes: 16c72e40 ("IB/cm: Refactor to avoid setting path record software only fields")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>