IB/mthca: Simplify CQ cleaning in mthca_free_qp()

IB/mthca: Simplify CQ cleaning in mthca_free_qp()

mthca_free_qp() already has local variables to hold the QP's send_cq
and recv_cq, so we can slightly clean up the calls to mthca_cq_clean()
by using those local variables instead of expressions like
to_mcq(qp->ibqp.send_cq).

Also, by cleaning the recv_cq first, we can avoid worrying about
whether the QP is attached to an SRQ for the second call, because we
would only clean send_cq if send_cq is not equal to recv_cq, and that
means send_cq cannot have any receive completions from the QP being
destroyed.

All this work even improves the generated code a bit:

add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-5 (-5)
function                                     old     new   delta
mthca_free_qp                                510     505      -5

Signed-off-by: Roland Dreier <rolandd@cisco.com>