systemc: Adjust some type names in a couple tests.

systemc: Adjust some type names in a couple tests.

These names happened to collide with names from gem5 itself, and when
linked together produced strange and incorrect results.

Ideally gem5's names should go inside a gem5 namespace, but that's a
much larger change.

Change-Id: Ie7c5f2236678d5dbb722a86321296fce395fbd37
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32175
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>