systemc: Stop using python init to set up predefined message ids.

We can now be sure register_id will work even mid static initializers,
so we don't have to use python initialization as a hook to install
these predefined message ids.

Change-Id: I2e4d0c678ddda0a9ce5b114bdf1710f36e955f23
Reviewed-on: https://gem5-review.googlesource.com/c/13976
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
2 files changed