For secure boot, a header is used to identify key table, signature
and image address. A new header structure is added for lsch3.

Currently key extension (IE) feature is not supported. Single key
feature is not supported. Keys must be in table format. Hence, SRK
(key table) must be present. Max key number has increase from 4 to
8. The 8th key is irrevocable. A new barker Code is used.
Signed-off-by: NAneesh Bansal <aneesh.bansal@nxp.com>
Signed-off-by: NSaksham Jain <saksham.jain@nxp.com>
Reviewed-by: NYork Sun <york.sun@nxp.com>