arch,cpu: Turn the Decoder objects into SimObjects.

Change-Id: I85839880db588b3b92064b8fcbf053c1811a1fdc
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52080
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
30 files changed