helper.h: note about hybrid CPUs in the distrib APIJust like in the hwloc-distrib manpage since edf08ec9f091f34824ad34cdbcbc0c109457f62dSigned-off-by: Brice Goglin <Brice.Goglin@inria.fr>(cherry picked from commit 4f2813fa6141aa3a867de8de70536e0c003a006d)