systemc: Generalize ignoring info messages in the reference output.

systemc: Generalize ignoring info messages in the reference output.

Those messages are very implementation specific and don't (generally)
affect correctness. This makes it easier to ignore info messages based
on their number.

This change also makes the output checker ignore a similarly styled
message gem5 generates. We should consider making gem5 not generate
that message and have it generate another message instead which is
specific to gem5. We would need to filter that out too when comparing
results.

Change-Id: I93b9e2d547b6259512db091cfc557d21f86f4a3d
Reviewed-on: https://gem5-review.googlesource.com/12086
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>