board/lsi: Redundant/Secure Boot Updates

1) Don't boot a non-secure image if secure
   boot is enabled.
2) Use U-Boot image files when creating signed,
   and possibly encrypted, images.

Signed-off-by: John Jacques <john.jacques@lsi.com>
board/lsi: fix single SMEM operation when DDR Retention enabled

Signed-off-by: Gary McGee <gary.mcgee@lsi.com>
Defect 48481: Power down HSS0-4 lanes after download of images using EIOA.

Signed-off-by: Jay Jayatheerthan <jay.jayatheerthan@lsi.com>