[SCSI] bnx2fc: Fix FW assert during RSCN stress tests

Firmware asserts when the same CQE is armed twice. This scenario happens during
RSCN stress tests as driver incorrects arms the CQ after the session is
offloaded.

Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>