scsi: qedi: Add support for Boot from SAN over iSCSI offload

This patch adds support for Boot from SAN over iSCSI offload. The iSCSI
boot information in the NVRAM is populated under
/sys/firmware/iscsi_bootX/ using qed NVM-image reading API and further
exported to open-iscsi to perform iSCSI login enabling boot over offload
iSCSI interface in a Boot from SAN environment.

Signed-off-by: Arun Easi <arun.easi@cavium.com>
Signed-off-by: Andrew Vasquez <andrew.vasquez@cavium.com>
Signed-off-by: Manish Rangankar <manish.rangankar@cavium.com>
Signed-off-by: Nilesh Javali <nilesh.javali@cavium.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>