cnic: Return error code in cnic_cm_close() if unsuccessful.

So that bnx2i can handle the error condition immediately and not have to
wait for timeout.

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