RDMA/rxe: Save a few bytes from struct rxe_pool

'table_size' is never read, it can be removed.

In fact, the only place that uses something that could be 'table_size' is
'alloc_index()'. In this function, it is re-computed from 'min_index' and
'max_index'.

Link: https://lore.kernel.org/r/2c42065049bb2b99bededdc423a9babf4a98adee.1635093628.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>