IB/netlink: Remove superfluous RDMA_NL_GET_OP() masking

'op' is the already RDMA_NL_GET_OP() masked 'type'.  No need to mask it again.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>
Acked-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>