To reproduce this panic consistently, we run an intensive network
application like 'netperf'. After waiting for a couple of seconds,
you will see a stack trace and a kernel panic where we are calling
pci_unmap_single() in ql_poll().

Changes:
1)  Check the flags on the Response MAC IO Control block to check for
errors
2)  Ensure that if we are on the 4022 we only use one segment
3)  Before, we were reading the memory mapped producer index register
everytime we iterated in the loop when clearing the queue.  We should
only be iterating to a known point, not as the producer index
is being updated.

Signed-off-by: Benjamin Li <benjamin.li@qlogic.com>
Signed-off-by: Ron Mercer <ron.mercer@qlogic.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>