systemc: Add a mechanism for pre-registering message type ids.

systemc: Add a mechanism for pre-registering message type ids.

These ids are the ones the Accellera implementation/tests use. Some of
the tests expect them to be available and usable.

Change-Id: I4e4dc3470c28d4113330a44ccd06ffe7724e75b1
Reviewed-on: https://gem5-review.googlesource.com/c/13322
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>