tools/power/x86/intel-speed-select: Increase number of CPUs displayed

Currently max 128 CPUs can be displayed in the enable CPU list. Double
the range. Since the size is big for stack allocation, change to static.
Here changing to static is fine as these functions are called in serial.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>