perf/x86/rapl: Rename 'maxdie' to nr_rapl_pmu and 'dieid' to rapl_pmu_idx

AMD CPUs have the scope of RAPL energy-pkg event as package, whereas
Intel Cascade Lake CPUs have the scope as die.

To account for the difference in the energy-pkg event scope between AMD
and Intel CPUs, give more generic and semantically correct names to the
maxdie and dieid variables.

No functional change.

Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20240502095115.177713-2-Dhananjay.Ugwekar@amd.com