arm: mach-k3: Add secure device support

K3 devices have High Security (HS) variants along with the non-HS already
supported. Like the previous generation devices (OMAP/Keystone2) K3
supports boot chain-of-trust by authenticating and optionally decrypting
images as they are unpacked from FIT images. Add support for this here.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Andreas Dannenberg <dannenberg@ti.com>