ARM: AM43xx: Enable post-processing of FIT artifacts loaded by U-Boot

ARM: AM43xx: Enable post-processing of FIT artifacts loaded by U-Boot

Enable the platform-specific post-processing of FIT-extracted blobs such
as Kernel, DTB, and initramfs on TI AM43xx high-security (HS) devices
which will ultimately invoke a ROM-based API call that performs secure
processing such as blob authentication.

Signed-off-by: Andreas Dannenberg <[email protected]>
Signed-off-by: Andrew F. Davis <[email protected]>
Reviewed-by: Lokesh Vutla <[email protected]>
Reviewed-by: Tom Rini <[email protected]>