RDMA/rxe: Compute the maximum sges and inline size based on the WQE size

RDMA/rxe: Compute the maximum sges and inline size based on the WQE size

The SGE buffer size and max_inline data should be derived from the size of
the WQE. Each value individually sets the WQE size, so compute the actual
sizes based on the actual WQE size and configure the QP with the maximums.

Also fix the missing return of the actual maximum capability to the caller.

Link: https://lore.kernel.org/r/1578962480-17814-3-git-send-email-rao.shoaib@oracle.com
Signed-off-by: Rao Shoaib <rao.shoaib@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>