Perf Changes For Linux 5.9 Include Intel Arch LBR, Hygon RAPL, Comet Lake Uncore

The Linux perf events changes for the performance monitoring subsystem were already sent in and pulled for the in-development Linux 5.9 kernel.

Among the changes this time around include:

- Intel Architectural LBR support for allowing the perf subsystem to keep track of the "last branch records" for the branches taken in control flow for easier analysis/profiling. The perf subsystem has already provided similar functionality using model specific registers while now Intel has been spinning the LBR support into an "architectural" feature for handling it without relying upon model-specific data.

- Runtime Average Power Limiting (RAPL) support for Hygon Family 18h CPUs (the Chinese Zen EPYC CPUs). The Linux kernel for a while has had most of the Hygon support in order while this RAPL support was one of the missing bits where it just needed the proper IDs added.

- Uncore (system agent) support for Intel Comet Lake. The uncore perf support on Comet Lake is another generation very similar to Skylake but just needed the new IDs added.

- Intel IIO stack to PMON mapping support for Skylake-SP processors for per-device performance counters and perf stat --iiostat support.

- Other smaller updates and other fixes.

More details within the pull request.