RDMA: Remove uverbs cmds from drivers that don't use them

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.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>