Adds support for loading Linux kernels through FIT payloads. This has been implemented as an assembly function in order to simplify dealing with some of the intricacies of loading a kernel (such as needing to jump to the kernel in ARM mode and the kernel ABI). TEST: Booted a FIT image containing a 5.4 kernel and initramfs on the Beaglebone Black. Change-Id: I7dbf9467665ec17447cec73676763844b4be4764 Signed-off-by: Sam Lewis <sam.vr.lewis@gmail.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/45335 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Julius Werner <jwerner@chromium.org>