Support for access to various energy and perf registers via papi

Issue

• Kernel support for rw access to various energy and perf registers in papi.
• Users need a way to measure perf on CPUs with possibly changing clock cycles.
• Provide a means to access the RAPL data without necessarily giving direct access to the MSRs.
• There are a lot of precedents of making data like this available using perf and PAPI.