RDMA/core: Avoid holding lock while initializing fields on stack

In various functions rdma_cm_event is zero initialized on stack using
memset() while holding lock which is not necessary.
Therefore, don't hold the lock while initializing on stack.

Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>