IB/mad: Don't discard BMA responses in kernel

This fixes the problem of incoming BMA responses being dropped due to
a bad "is response" check.  Fix the test to use the ib_response_mad()
predicate, which correctly handles BMA MADs.

This fixes <https://bugs.openfabrics.org/show_bug.cgi?id=988>.
Signed-off-by: Michael Brooks <michael.brooks@qlogic.com>
Acked-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/mad.c

@@ -1697,9 +1697,8 @@ static inline int rcv_has_same_gid(struct ib_mad_agent_private *mad_agent_priv,
 	u8 port_num = mad_agent_priv->agent.port_num;
 	u8 lmc;
 
-	send_resp = ((struct ib_mad *)(wr->send_buf.mad))->
-		     mad_hdr.method & IB_MGMT_METHOD_RESP;
-	rcv_resp = rwc->recv_buf.mad->mad_hdr.method & IB_MGMT_METHOD_RESP;
+	send_resp = ib_response_mad((struct ib_mad *)wr->send_buf.mad);
+	rcv_resp = ib_response_mad(rwc->recv_buf.mad);
 
 	if (send_resp == rcv_resp)
 		/* both requests, or both responses. GIDs different */