Use physinfo.max_cpu_id instead of physinfo.nr_cpus to get max CPU id.
This fixes for example 'xenpm get-cpufreq-para' with smt=off, which
otherwise would miss half of the cores.
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>