RDMA/rxe: Remove redundant scheduling of rxe_completer

RDMA/rxe: Remove redundant scheduling of rxe_completer

In rxe_post_send_kernel() if the qp is in the error state after posting
the work requests the rxe_completer() task is scheduled.

But, the only way to move the qp into the error state is to call
rxe_qp_error() which also schedules the rxe_completer() task to drain the
queues. Calling it a second time has no effect. This commit removes the
redundant call.

Link: https://lore.kernel.org/r/20240329145513.35381-6-rpearsonhpe@gmail.com
Signed-off-by: Bob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>