[SCSI] bnx2: Add support for CNIC driver.

Add interface and functions to support a new CNIC driver to drive
the Broadcom bnx2 hardware for iSCSI offload.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>