perf/x86/rapl: Refactor to share the RAPL code between Intel and AMD CPUs

This patch modifies the rapl_model struct to include architecture specific
knowledge in this previously Intel specific structure, and in particular
it adds the MSR for POWER_UNIT and the rapl_msrs array.

No functional changes.

Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200527224659.206129-3-eranian@google.com