misc,cpu: Make ThreadContext work with PCStateBase-s.

Change-Id: I92f1d79c697bb45f610604c9e84b24ea93d58776
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52058
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
53 files changed