be2net: Fix to avoid firmware update when interface is not open.

Since interrupts are enabled only when open is called on the interface,
Attempting a firmware update operation when interface is down could lead to
partial success or failure of operation. This fix fails the request if
netif_running is false.

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