Get rid of VecRegT, and a few redundant or unused methods. Change-Id: I6c88c40653e1939fe74b8ffb847ef50ab8064670 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/41995 Reviewed-by: Gabe Black <gabe.black@gmail.com> Maintainer: Gabe Black <gabe.black@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com>