sim: Convert stat functions to use VPtr.
sim: Convert stat functions to use VPtr.

Change-Id: I1fe43ad7508b5fbbcbf6c84195858455fc8f3e85
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/29402
Reviewed-by: Matthew Poremba <f1eb50f3368ce197c52b19f7fdb5aa7a278f15fd@amd.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5