Interrupt ack fixes

Fix the packet count resets at interrupt time, using the cacheable
packet count status to set number of processed/received packets, since
the ack count is the cumulative number of packets processed, and not
incremental.
Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Jeff Garzik <jeff@garzik.org>