spl: fdt: Record load/entry fit-images entries in 64bit format

spl: fdt: Record load/entry fit-images entries in 64bit format

The commit 221eb7c2870e ("spl: fit: implement fdt_record_loadable") which
introduced fdt_record_loadable() state there spl_fit.c is not 64bit safe.
Based on my tests on Xilinx ZynqMP zcu102 platform there shouldn't be a
problem to record these addresses in 64bit format.
The patch adds support for systems which need to load images above 4GB.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>