bnx2x: EEH recovery fix

When EEH detects an i/o error it resets the device thus it cannot be accessed.
In this case the driver needs to unload its interface only with OS, kernel and
network stack but not with the device.
After successful recovery, the driver can load normally.

Signed-off-by: Yitchak Gertner <gertner@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>