systemc: Make a test use cout for all its messages.

systemc: Make a test use cout for all its messages.

This makes them end up in simout so verify.py can find them when it's
checking output.

Change-Id: I2b7b276b3e1816a257f58b0cfb13487d6296e6fd
Reviewed-on: https://gem5-review.googlesource.com/12216
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>