bnx2x: Calling napi_del

rmmod might hang without this patch since the reference counter is not going
down

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>