IB/mthca: Don't execute QUERY_QP firmware command for QP in RESET state

If a QP being queried is in the RESET state, don't execute the
QUERY_QP firmware command (because it will fail).

Signed-off-by: Dotan Barak <dotanb@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>