misc: Tagged API methods in sim/drain.hh

Change-Id: Id584d0be027048064d5f650ae0f2ea5a7f075a47
Issue-on: https://gem5.atlassian.net/browse/GEM5-172
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27988
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed