tools/power/x86/intel-speed-select: Use core count for base-freq mask

Some firmware implementation gives error when a command is sent get mask
for core count 32-61. So use core count to decide.

But there is no function to get core count. So introduce one function to
get core count.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>