To support the trust boot chain, we integrate the authentication
into the kernel image loading process. The kernel image will be verified
at its load address. So when signing the kernel image, we need to
use this load address which may change on different platforms.

Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 3c118b8d6bbe1a25ca8c8bafeb528309f16fc73d)