cpupower tools: Fix malloc of cpu_info structure

The cpu_info member of cpupower_topology was being declared as an unnamed
structure. This member was then being malloced using the size of the
parent cpupower_topology * the number of cpus. This works
because cpu_info is smaller than cpupower_topology. However, there is
no guarantee that will always be the case. Making cpu_info its own
top level structure (named cpuid_core_info) allows for mallocing the actual
size of this structure. This also lets us get rid of a redefinition of
the structure in topology.c with slightly different field names.

Signed-off-by: Palmer Cox <p@lmercox.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>