cnic, bnx2i: Fix bug on some bnx2x devices that don't support iSCSI

On some bnx2x devices, iSCSI is determined to be unsupported only after
firmware is downloaded.  We need to check max_iscsi_conn again after
NETDEV_UP and block iSCSI init operations.  Without this fix, iscsiadm
can hang as the firmware will not respond to the iSCSI init message.

Signed-off-by: Eddie Wai <eddie.wai@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>