examples/vm_power: respect maximum CPUs

examples/vm_power: respect maximum CPUs

The vm_power_manager app was not respecting the POWER_MGR_MAX_CPUS
during initialisation, so if there were more CPUs than this value (64),
it would lead to buffer overruns of there were more then 64 cores in
the system.

Added in a check during init and un-init to only initialise up to
lcore_id 63.

This raises the question as to why not simply increase the value of
POWER_MGR_MAX_CPUS. Well, it's not that simple, as many of the APIs take
a uint64_t as a parameter for the core mask, and this will not work for
cores greater than 63. So some work needs to be done in the future to
remove this limitation. For now we'll fix the memory corruption.

Also, the patch that this fixes says "allow greater than 64 cores" but
that's not across the entire application, it's only for the out-of-band
monitoring. I'll add a notice for an API change in the next release to
clean this up, i.e. depricate any API calls that use masks.

Fixes: 6453b9284b64 ("examples/vm_power: allow greater than 64 cores")
Cc: stable@dpdk.org
Signed-off-by: David Hunt <david.hunt@intel.com>