Allowing userspace to invoke these commands is probably going to crash
these drivers as they are not tested and not expecting to use them on a
user object.

For example pvrdma touches cq->ring_state which is not initialized for
user QPs.

These commands are effected:

- IB_USER_VERBS_CMD_REQ_NOTIFY_CQ is ibv_cmd_req_notify_cq() in
  rdma-core, only hfi1, ipath and rxe calls it.

- IB_USER_VERBS_CMD_POLL_CQ is ibv_cmd_poll_cq() in rdma-core, only
  ipath and hfi1 calls it.

- IB_USER_VERBS_CMD_POST_SEND/RECV is ibv_cmd_post_send/recv() in
  rdma-core, only ipath and hfi1 call them.

- IB_USER_VERBS_CMD_POST_SRQ_RECV is ibv_cmd_post_srq_recv() in
  rdma-core, only ipath and hfi1 calls it.

- IB_USER_VERBS_CMD_PEEK_CQ isn't even implemented anywhere

- IB_USER_VERBS_CMD_CREATE/DESTROY_AH is ibv_cmd_create/destroy_ah() in
  rdma-core, only bnxt_re, efa, hfi1, ipath, mlx5, orcrdma, and rxe call
  it.

Link: https://lore.kernel.org/r/10-v1-caa70ba3d1ab+1436e-ucmd_mask_jgg@nvidia.comSigned-off-by: Jason Gunthorpe <jgg@nvidia.com>