tools/power/turbostat: split core MSR support into status + limit

Some CPUs may not have PP0/Core domain power limit MSRs. We
should still allow its domain energy status to be used. This
patch splits PP0/Core RAPL into two separate flags for power
limit and energy status such that energy status can continue
to be reported without power limit.

Without this patch, turbostat will not be able to use the
remaining RAPL features if some PL MSRs are not present.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>