arch-vega: Simplify VecRegContainer in Vega

VecRegContainer was simplified in [1] while the Vega patches were still
under review so the changes in [1] were not applied to arch-vega.

[1] https://gem5-review.googlesource.com/c/public/gem5/+/41995

Change-Id: I350ac94dc14e3ba0fb9619fa084e80cc8cbd7660
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47100
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
2 files changed