bnx2x: Block nvram access when the device is inactive

Don't dump eeprom when bnx2x adapter is down.  Running ethtool -e causes an eeh
without it when the device is down

Signed-off-by: Paul Larson <pl@linux.vnet.ibm.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>