RDMA/cxgb4: Remove the query_pkey callback

Now that the query_pkey() isn't mandatory by the RDMA core for iwarp
providers, this callback can be removed.

Link: https://lore.kernel.org/r/20200714183414.61069-6-kamalheib1@gmail.com


Signed-off-by: Kamal Heib <kamalheib1@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>