RDMA/cm: Add missing locking around id.state in cm_dup_req_handler

All accesses to id.state must be done under the spinlock.

Fixes: a977049d

 ("[PATCH] IB: Add the kernel CM implementation")
Link: https://lore.kernel.org/r/20200310092545.251365-10-leon@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>