The fast_registration length is used to convey length for memory
registrations through UMR which can be of any size up to 2^64.
Change the length type to be u64.
Fixes: 968e78dd96 ('IB/mlx5: Enhance UMR support to allow partial page table update')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>