RDMA/mlx5: Remove FMR leftovers

Remove a few leftovers from FMR functionality which are no longer used.

Link: https://lore.kernel.org/r/5-v3-f58e6669d5d3+2cf-fmr_removal_jgg@mellanox.com


Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Acked-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>