RDMA/rxe: Generate error completion for error requester QP state

RDMA/rxe: Generate error completion for error requester QP state

As per IBTA specification, all subsequent WQEs while QP is in error state
should be completed with a flush error.

Here we check QP_STATE_ERROR after req_next_wqe() so that rxe_completer()
has chance to be called where it will set CQ state to FLUSH ERROR and the
completion can associate with its WQE.

Link: https://lore.kernel.org/r/1658307368-1851-3-git-send-email-lizhijian@fujitsu.com
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>