RDMA/rxe: Use the correct size of wqe when processing SRQ

RDMA/rxe: Use the correct size of wqe when processing SRQ

The memcpy() that copies a WQE from a SRQ the QP uses an incorrect size.
The size should have been the size of the rxe_send_wqe struct not the size
of a pointer to it. The result is that IO operations using a SRQ on the
responder side will fail.

Fixes: ec0fa2445c18 ("RDMA/rxe: Fix over copying in get_srq_wqe")
Link: https://lore.kernel.org/r/20210729220039.18549-2-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>