cnic: Fix rare race condition during iSCSI disconnect.

If the initiator and target try to close the connection at about the same
time, there is a race condition in the termination sequence for bnx2x.
Fix the problem by waiting for the remote termination to complete before
deleting the Connection ID.  This will prevent the firmware assert.

Update version to 2.5.15.

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>