cnic: set error flag when iSCSI connection fails

to speed up error recovery due to SPQ failures.  The error flag will
expedite the recovery process by skipping the timeouts.

Signed-off-by: Jeffrey Huang <huangjw@broadcom.com>
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>