systemc: Add a nonstandard sc_status pretty printer operator.

systemc: Add a nonstandard sc_status pretty printer operator.

This operator exists in the Accellera implementation, and is necessary
to make the test output match.

Change-Id: I266629d6c936d4846e88e35af36555fb392b181c
Reviewed-on: https://gem5-review.googlesource.com/12074
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>