RDMA/rxe: Move max_elem into rxe_type_info

Move the maximum number of elements from a parameter in rxe_pool_init to a
member of the rxe_type_info array.

Link: https://lore.kernel.org/r/20220304000808.225811-7-rpearsonhpe@gmail.com


Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>