This ancient and unsafe method for memory registration is no longer used
by any RDMA based ULP. Remove the FMR pool API from the core driver.

Link: https://lore.kernel.org/r/4-v3-f58e6669d5d3+2cf-fmr_removal_jgg@mellanox.comSigned-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>