RDMA/rxe: Change variable and function argument to proper type

The type of wqe length is u32 so in order to avoid overflow and shadow
casting change variable and relevant function argument to proper type.

Link: https://lore.kernel.org/r/20220307145047.3235675-1-cgxu519@mykernel.net


Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>