systemc: Make some tests use cout instead of cerr to report completion.

systemc: Make some tests use cout instead of cerr to report completion.

cerr goes to simerr, but we compare simout against the golden output.

Change-Id: I9270866a92dd06a23d47c1964dacc4872030f30d
Reviewed-on: https://gem5-review.googlesource.com/c/12470
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>