The driver puts the device into MAC loopback in two places in the
driver.  This patch consolidates the code into a single routine.
Signed-off-by: NMatt Carlson <mcarlson@broadcom.com>
Reviewed-by: NMichael Chan <mchan@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>