RX error count is injected in the old shared memory in the field named
        "rx_bad_count". The old system requires to reset this counter if the
        rx_error count doesn't increase. Thus, wee need to compare the current
        rx_err counter to the previous one in order to publish the real number
        of errors or 0. This implementation was not supporting multiple segment
        in the same process, because the previous err counter was kept as a
        static variable. This counter is moved into masterfip device.

Signed-off-by: Michel Arruat <michel.arruat@cern.ch>