platform/x86/intel/ifs: Update documentation with image download path

The documentation previously listed the path to download In Field Scan
(IFS) test images as "TBD".

Update the documentation to include the correct image download
location. Also move the download link to the appropriate section within
the documentation.

Reported-by: Anisse Astier <anisse@astier.eu>
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Link: https://lore.kernel.org/r/20250131205315.1585663-1-jithu.joseph@intel.com


Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>