RDMA/mlx5: Remove set but not used variables

Remove "uctx" and "pa" variables that were set but not used.

Fixes: a8b92ca1 ("IB/mlx5: Introduce DEVX")
Fixes: 8f062287 ("RDMA/mlx5: Remove debug prints of VMA pointers")
Signed-off-by: Kamal Heib <kamalheib1@gmail.com>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>