IB/ipath: Generate flush CQE when QP is in error state

Follow the IB spec. (C10-96) for post send which states that a flushed 
completion event should be generated for work requests posted when a QP
is in the error state.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>