be2net: Bug fix to avoid soft lockup in loopback test.

This change ensures that loopback test command gives up after 4 seconds when
the hardware is not responsive. This could happen if the ports are connected
properly in loopback mode.

Signed-off-by: Sarveshwar Bandi <sarveshwarb@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>