arch,cpu: Use PCStateBase for decoder methods.

Change-Id: I79f1c5dd39de7015a5c5b891e1888d9a176bb5b4
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52063
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
13 files changed