tools/power turbostat: show missing Core and GFX power on SKL and KBL

While the current SDM is silent on the matter, the Core and GFX
RAPL power meters on SKL and KBL appear to work -- so show them.

Reported-by: Yaroslav Isakov <yaroslav.isakov@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>