RDMA/core: Use simpler spin lock irq API from blocking context

add_client_context(), ib_unregister_device() and ib_unregister_client()
are designed to call from blocking context.  There is no need to save and
restore last interrupt state when called from such blocking context.  Even
though this is not a performance path, using the right spin lock API is
desired for code clarity.

To avoid checkpatch warning while removing flags, sizeof() is used.

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>