systemc: Update some defaults in verify.py.

systemc: Update some defaults in verify.py.

Change the defaults in verify.py to be more like how I've been running
it. This is as close of an approximation as I have to how someone else
would want to run it manually. When run as part of a script, it's less
cumbersome to have to add extra arguments.

Change-Id: Ibd7c7168a38aa5c014ab5c1246c9617c7358e4f9
Reviewed-on: https://gem5-review.googlesource.com/c/12602
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>