systemc: Add an sc_gen_unique_name namespace to processes as well.

systemc: Add an sc_gen_unique_name namespace to processes as well.

The standard says that there are namespaces for each module, and
one global namespace. Accellera also has namespaces for each process,
which shows up in the test output.

Change-Id: I4c8c5cecd5fb685d7bab521d9ae131aef23a6ab4
Reviewed-on: https://gem5-review.googlesource.com/c/13291
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>