RDMA/rxe: Move atomic original value to res

Move the saved original value to the atomic responder resource.  This
replaces saving it in the qp. In preparation for merging the normal and
retry atomic responder flows.

Link: https://lore.kernel.org/r/20220606143836.3323-5-rpearsonhpe@gmail.com


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