Fixed so it works on the PE-800.  It had not previously been updated to
match PE-800 receive interrupt differences from HT-400.
Signed-off-by: Bryan O'Sullivan <bos@pathscale.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
 
        if (tail == head) {
                set_bit(IPATH_PORT_WAITING_RCV, &pd->port_flag);
+               if(dd->ipath_rhdrhead_intr_off) /* arm rcv interrupt */
+                       (void)ipath_write_ureg(dd, ur_rcvhdrhead,
+                                              dd->ipath_rhdrhead_intr_off
+                                              | head, pd->port_port);
                poll_wait(fp, &pd->port_wait, pt);
 
                if (test_bit(IPATH_PORT_WAITING_RCV, &pd->port_flag)) {